
\Add/Edit External Command

The Add a New Command operation button lets you add new
external commands to the command list.  Selecting the Add a
New Command button displays the Add External Command dialog
box.  This box allows you to set up the new command.

\Add New Material

The Add New Material dialog box permits you to add a new
material to the materials library.  The initial properties
of the new material are copied from an existing library
material.

\Adding a Light

The Add Light option lets you add a new light to the list of
currently defined lights.  Selecting Add Light activates the
Add Light dialog box.  This box allows you to define all
parameters associated with the new light.

\Adding a View

The Add a View option of the Views menu lets you add a new
view to the end of the view list.  If no views are in the
list, this option creates the first view.

Selecting Add a View activates the Add View dialog box. This
box allows you to adjust the target and camera coordinates,
introduce a front clipping plane (a cropping feature), and
ask BIG D to generate additional frames between views.

Once you have the new view defined to your liking, select
the OK button to add the view to the end of the view list.
The Add View dialog box will disappear and you can now
access the menu bar.

Selecting Cancel to exit the Add View dialog box will exit
the box without adding the new view to the end of the view
list.

\Adjusting the Camera

Below the target buttons are six buttons which allow you to
adjust the location of the camera.  The four single arrow
buttons rotate the location of the camera a small amount
around the target location.

Selecting the up arrow will rotate the camera upward about
the target. This enables you to view the model from a higher
elevation.  The left, right, and down arrows rotate the
camera equal amounts in each respective direction.

The two double arrow buttons on the button panel move the
camera closer to or farther away from the target location.
These buttons are called the camera zoom buttons.

The left button (with the inward pointing arrows) is the
zoom-in button.  Each press of the button causes the camera
to move about 10 percent closer to the target while
maintaining the same orientation.

The right button (with the outward pointing arrows) is the
zoom-out button.  It moves the camera about 10 percent
farther away from the target for each button press.

\Adjusting the Target

At the top of the button panel are four buttons which allow
you to adjust the location of the target.  Each button will
rotate the location of the target a small amount around the
camera location.

Selecting the up arrow will rotate the target upward about
the camera. This causes your center of view to move upward.
The left, right, and down arrows move the target equal
amounts in each respective direction.

NOTE: When you select the right arrow the objects in the
projection will appear to move to the left.  At first this
may appear to be opposite of what should happen.  Keep in
mind that it is the target that you are moving, not the
model.

\Ambient Light

Ambient light is background light which is applied to all
surfaces equally, regardless of location or orientation.
Ambient light is used to simulate light which is reflected
from the atmosphere and other objects in the scene.

Without ambient light, surfaces which are shaded from all
other light sources will appear totally black.  Therefore,
the ambient light's primary purpose is to illuminate
surfaces which are in shade.  If shaded surfaces are being
rendered too dark, you should increase the ambient light
intensity.

The ambient light has no location or direction and is not
part of the light list.  Ambient light will only illuminate
materials which have a non-zero ambient reflection
coefficient.

The ambient light's color and intensity can be set by
selecting the Ambient Light option from the Lights menu.
Three slide bars are available for adjusting the light's
hue, saturation, and intensity. The hue and saturation can
also be set using the Select Color operation button.

The ambient light's intensity is measured as an absolute
number from 0 to 100 (not a percentage).  Typical intensity
values for the ambient light vary from 10 to 20.

\Ambient Reflection

The ambient reflection coefficient sets the percentage of
ambient (background) light a material reflects.  Typical
values range from 10 to 20 percent.  

Ambient light is background light, applied evenly to all
surfaces regardless of orientation.  The ambient reflection
coefficient effectively determines how light or dark a
material will be when it is in total shade.

Without ambient light, surfaces shaded from all other lights
would receive no light and appear black.  See the Lights
chapter for details about ambient light.

\Angular Precision

Angular precision sets the precision with which angular
measurements are displayed.  For decimal degrees, radians,
and gradians this is the number of decimal places displayed.
For degrees/minutes/seconds this sets the accuracy of the
angle displayed.

\Angular Units

Angular units are used to display all angular measurements.
Select your preference of decimal degrees, radians,
degrees/minutes/seconds, or gradians.

\Antialiasing

Antialiasing (anti-alias-ing) is a feature designed to
smooth out or nullify "aliasing", a characteristic of raster
graphics devices.  In order to draw a diagonal line or edge,
a raster graphics device must stairstep to conform to the
pixel grid, resulting in "aliasing", or the "jaggies".  

With Antialiasing turned on, BIG D attempts to compensate
for these jagged edges by averaging each pixel with adjacent
pixels.

Antialiasing does not affect image generation time.

\Arc Resolution

The Arc Resolution option determines how curved surfaces are
represented in plan, elevation, and wire-frame views. Curved
surfaces are approximated by flat polygons in wire-frame
views.  The arc resolution sets how many polygons represent
each surface.

Low Arc Resolution uses a minimum number of polygons to
represent each curved surface.  This gives a rough
approximation, but allows fast regenerate and redraw times.


High Arc Resolution uses a maximum number of polygons and
generates the best looking curves, but has the slowest
redraw time.  The Medium setting is a compromise between the
two extremes.

\Assign Material to Layer

To assign a different material to the current layer, select
the "Assign Material to Current Layer" button.  The Layers
dialog box disappears and is replaced by the Assign Material
dialog box.

The Assign Material dialog box displays the name of the
current layer in the title.  Below the title is the name of
the material which is currently assigned to the layer.

Below the current material line is the materials scroll box.
The materials scroll box contains a list of the names of all
materials which are in the materials library.  The name of
the currently assigned material is highlighted in the scroll
box.

To select a different material, scroll through the list of
materials until the material appears in the box.  Move the
cursor to the line the material name is on and press the
left mouse button.

The material selected will highlight and the current
material above will change to the newly selected material.

Select the OK button to confirm the new material assignment.
The Assign Material dialog box will disappear and the Layers
box will reappear.  The newly selected material will now
show up on the current layer line.

Selecting the CANCEL button in the Assign Material dialog
box will discard any changes and return to the Layers dialog
box.

\Background Color

The background color dialog box sets the intensity of any
image pixel which does not intersect an object in the scene.
Select the Background Color item from the Options menu to
display the Background Color dialog box.

The Background Color dialog box offers three slide bars and
one operation button for setting background color.  The
slide bars allow you to set the hue, saturation, and
intensity of the background color. The operation button lets
you set both hue and saturation using the color selection
screen on the rendering device.

\Background Hue

The background hue is the color of the background.  It is
defined as an angle between 0 and 360 degrees.  The angle
corresponds to a color on a color wheel, with red at 0
degrees, green at 120 degrees, and blue at 240 degrees.

You can select the background hue by picking an angle on the
hue slide bar or by using the color selection screen (see
Select Color).

\Background Intensity

The background intensity is a measure of the brightness of
the background.  It is an absolute number (not a percentage)
from 0 to 100.  The higher the number, the brighter the
background.

To set the background color, first set the intensity level
using the intensity slide bar.  Then pick the Select Color
button to choose the hue and saturation of the background
color.  See the Interface chapter for details on using the
color selection screen.

NOTE: When using the Select Color operation, if the color
selection rectangle on the rendering device appears black,
it probably indicates the intensity is set to zero.  Be sure
to set intensity to a non-zero value before using the Select
Color operation. 

\Background Saturation

Saturation is the purity or vividness of the color, measured
as a value between 0 and 100 percent.  A pure color is 100%
saturated.  As white is added, saturation decreases.  Zero
saturation gives no color at all, a shade of gray.  

You can select the background's saturation by picking an
percentage on the saturation slide bar or by using the color
selection screen (see Select Color).

\Base Output File Name

BIG D generates a rendering for every view that is currently
defined. It also generates additional frames in between
defined views if you asked it to in the view dialog boxes.

Each view which is generated is stored on disk in a TARGA
format file. The name of each TARGA file depends on the base
output file name, the view number, and the additional frame
number (if any).

All output TARGA files will start with the the base output
file name. This name can be from one to four characters
long.  The default base output file name is taken from the
input DXF file name.  For example, if you are currently
working on the SAMPLE.DXF file, the default base output file
name will be "SAMP".

You can change the base output file name by typing in a new
base output file name.

A two digit number will be appended to the base output file
name for each view generated.  This number corresponds to
each view number which is defined.  For instance, if three
view are currently defined and the base output file name is
"SAMP", then the TARGA files generated for the three views
will be named "SAMP01.TGA", "SAMP02.TGA", and "SAMP03.TGA".

If additional frames between any two views have been
specified (in the View dialog box), BIG D will append an
additional two letter code onto the file name for each
additional frame.  The additional code begins with "AA",
"AB", "AC" and so on.

For example, if two additional frames have been requested
between view number one and view number two of the above
example, the additional TARGA files will be named
"SAMP01AA.TGA" and "SAMP01AB.TGA".

\Bits Per Pixel

Bits per Pixel tells BIG D how many bits of information are
needed to specify each pixel.  

If your rendering device is limited to 256 colors, you
should set Bits per Pixel to 8.  Rendering devices which are
limited to 256 colors include the IBM VGA and
AutoCAD/AutoShade ADI drivers.

If you are using a TARGA 16 or Vision 16, set this option to
16. TARGA 24, TARGA 32, Vision 32, and Vista users should
set Bits per Pixel to either 24 or 32.

NOTE: It is very important that you set Bits per Pixel
correctly.  An incorrect setting may not allow you to
display the rendered image on your rendering device.

\Camera Icon Size

The Camera Icon Size option sets the size of the camera icon
which is drawn in the view ports to represent the location
of a camera.  The camera icon is drawn as a square which
encloses the camera's view number.

The size of the camera icon is measured in pixels.

\Command

The Command line prompts you for the name of the actual
command which BIG D will use to execute the external
command.  This is the command you would type if you were
executing the command at the DOS prompt.

For instance, if you are adding an external command to load
AutoCAD, you would type "ACAD" at the Command line.

\Command Description

The Command Description line prompts you for a word or
phrase which describes the command you are editing.  This
description can be more meaningful than the command itself.

For example, if you are adding a command to load AutoCAD the
actual command is called "ACAD".  Your command description
can be a more descriptive phrase such as "Load AutoCAD".

\Commands Scroll Box

The Commands scroll box contains an alphabetical list of
commands created by the user for executing DOS commands or
programs outside of BIG D.  

The list actually contains a description of each command,
not the actual commands.  For example, the list may contain
a command called "Load AutoCAD".  The actual command used by
BIG D to execute this command may be simply "ACAD".

To select a current external command, move the cursor of the
line of the command you wish on which you wish to operate
and press the left mouse button.  If the list is too long to
fit in the box, you may need you use the scroll bar to
display the command you want.

Except for the Add operation, the operation buttons only
operate on the currently active external command.

\Configuring BIG D

Before you can run BIG D, you must configure BIG D to work
with your computer's hardware.  BIG D uses two types of
devices, a graphics device and a rendering device.  

*** The Graphics Device ***

The graphics device is used by BIG D's graphical user
interface (discussed in detail later) to interact with you.
All view ports, menus, and dialog boxes use the graphics
device.  This device typically uses from 2 to 16 colors.

*** The Rendering Device ***

The rendering device is used by BIG D to display finished
rendered images.  The rendering device requires the ability
to display at least 256 simultaneous colors.  The rendering
device may be the same as the graphics device.

*** BDSETUP ***

BDSETUP is the name of the BIG D configuration program.  The
INSTALL program calls BDSETUP automatically when it finishes
the installation of BIG D.

BDSETUP first lists all supported graphics devices.  Choose
the number of the adapter which matches your hardware.

BDSETUP then lists supported rendering devices.  Again, you
should choose the device you wish to use.

BDSETUP then asks if the graphics device and the rendering
device share the same screen.  Answer Yes or No.

Finally, BDSETUP displays your current choices and and asks
if they are correct.  If you answer No, BDSETUP repeats the
configuration questions.  If you answer Yes, BDSETUP saves
your responses in a configuration file (named BIGD.CFG
located in the BIG D directory) and returns to the DOS
prompt.

BIG D allows you to use the AutoCAD/AutoShade ADI driver
supplied with your graphics card as both the graphics and
rendering device.  If you select the ADI driver, BDSETUP
will ask for the interrupt number (in hexadecimal format)
which is used by the driver.  Refer to your graphics adapter
documentation for the correct interrupt number.

If you are going to use the ADI driver for the rendering
device, it must be a true 256 color driver.  ADI drivers
which use dithering to simulate 256 colors do NOT work with
BIG D.  Also, if you select the ADI driver as the graphics
device, you should also select the ADI driver as the
rendering device.  Using another rendering device along with
the ADI graphics device can cause problems with BIG D.

NOTE: If you are configuring the graphics device for EGA or
VGA and the rendering device for either the TARGA or Vision
boards, you may experience a problems if the TARGA or Vision
board is set to use memory segment A000.  This is because
both the EGA/VGA board and the TARGA/Vision board are using
the same memory locations.  The conflict can be resolved by
reconfiguring the TARGA or Vision board to use another
memory segment such as D000.  Refer to your TARGA or Vision
documentation for details.

You may reconfigure BIG D at any time by typing BDSETUP at
the DOS prompt.  Alternatively, you may also use the /C
switch when starting the BIG D program.  For example, if you
want to reconfigure BIG D before executing BIG D, type

    BIGD /C

BIG D will ask you the configuration question before
beginning execution.

\Copy From

The "Copy From" prompt displays the name of an existing
material on which you wish to base the new material.  BIG D
will copy the properties of the Copy From material to the
new material.

\Cross Cursor Size

The Cross Cursor Size option sets the size of the cross
cursor displayed when moving cameras, targets, and lights in
the view ports. The size is measured in pixels.

\Current Command

The Current Command line displays whatever command is
highlighted in the Commands scroll box immediately below. If
no command is highlighted or no commands are available, this
line is blank.

\Current File

The Current File line displays the currently opened DXF
file.  If no file is currently open, only the current drive
and directory are displayed.

Below the Current File line are three scroll boxes which
allow you to open a DXF file from anywhere on your system.

\Current Image

The Current Image line shows the name of the currently
active image file.  This is the file which is currently
highlighted in the File scroll box.  The Current Image line
includes the full path to the file.

\Current Layer

The Current Layer line displays the name of the layer which
is currently selected in the layers scroll box.

\Current Material

The Current Material line displays the name of the material
which is currently selected in the materials scroll box.

\Default Arguments

Below each prompt line is a line for the default command
line argument.  You can type defaults for each command line
argument.

When the command is executed, BIG D will automatically fill
in each command line argument line with the appropriate
default argument.  You are then free at that time to change
each argument to a new value.

When satisfied with your entry, select OK to add the new
command to the list of external commands, or select Cancel
to exit without saving the new command.  BIG D will
redisplay the External Commands dialog box.

\Default Colors

The default colors set the colors used in the drawing areas
of the view ports. The background color sets the background
of the drawing area.  The halftone color sets the color used
to draw normal icons. The forground color sets the color
used to draw selected or highlighted icons in the drawing
area.

Actual objects and entities in the model are drawn with the
color assigned to their assigned layers and are not affected
by the default colors.

\Delete Current Command

The Delete External Command operation button lets you delete
the currently selected external command from the command
list.

To delete the currently selected external command, select
the Delete External Command button.  A small dialog box
appears asking you to confirm your decision to delete the
external command.

Select Yes to delete the command from the external command
list, or pick No to keep the command in the list.

\Deleting an Existing Light

To delete one or more lights from the light list, pick the
Delete Existing Light option from the Lights menu.  BIG D
draws all current lights in the Plan and Elevation ports.  

You can then select each light to delete by positioning the
cursor over either its target or camera icon and pressing
the left mouse button.  Each selected icon will become
highlighted as it is chosen.

The selected lights are not actually deleted from the light
list until you pick the OK button.  Selecting the Cancel
button exits the light deletion mode without deleting any
lights.

\Deleting an Existing View

To delete one or more views from the view list, pick the
Delete Existing View option from the View menu.  BIG D draws
all current views in the Plan and Elevation ports.  

You can select each view to delete by positioning the cursor
over either its target or camera icon and pressing the left
mouse button. Each selected icon will become highlighted as
it is chosen.

The selected views are not actually deleted from the view
list until you pick the OK button.  Selecting the Cancel
button exits the view deletion mode without deleting any
view.

\Dialog Box Colors

The dialog box colors set the colors used to draw dialog
boxes.  The halftone color is used to draw dialog box
options which are disabled.

\Dialog Boxes

Most of BIG D's features are controlled through dialog
boxes.  Dialog boxes are composed of several types of
elements.  Which elements are used depends on the type of
data which needs to be entered.

The elements which can make up a dialog box include the
title, labels, buttons, text strings, slide bars, and scroll
boxes.

*** Box Title ***

Every dialog box has a title in the upper left hand corner.
The title provides a brief description of the purpose of the
box.

The title of a box may be selected with the mouse cursor to
obtain general information about the box.

*** Labels ***

Labels are descriptions of each element in the dialog box.
Labels are aligned in a column along the left side of the
dialog box.

Labels are text items which end with a colon (:).  The
element described by the label is usually located directly
to the right of the label.

Context sensitive help can be obtained about any item in a
dialog box by moving the mouse cursor over the item's label
and pressing the left mouse button.  

The current dialog box will temporarily disappear and a help
box will take its place.  The help box will contain
information about the labeled item which was selected.  When
you exit the help box, the previous dialog box is restored
so you can resume working.

*** Buttons ***

Buttons are used to set parameters where a limited number of
options exist.  A button is a small rectangular, shadowed
box.  A textual description of the button's value is
displayed on the button.

You can select a button using the mouse cursor.  When a
button is selected, it becomes highlighted (in reverse
video).  Buttons are grouped in sets and only one button in
a set can be selected at any time.

*** Scroll Boxes ***

Scroll boxes are used to select one item from a (possibly
long) list of items.  A scroll box consists of a title at
the top, a list of selectable items arranged in a column,
and a vertical scroll bar along the right.

The currently selected item in the list is highlighted in
reverse video.  You can select a different item using the
mouse cursor.

If the number of items in the list exceeds the number of
items which can fit in the box, you can use the scroll bar
along the right side of the box to scroll through the list.
The up and down arrows scroll the list one item at a time.
The scroll bar itself can be used to quickly jump to
different sections of the list.

*** Slide Bars ***

A slide bar is used to enter whole numbers within a finite
range.  A slide bar is similar in appearance and function to
a horizontal scroll bar.  It consists of a horizontal
sliding bar with left and right arrows at each end.  At the
far end of the slide bar is a number box showing the current
value of the slide bar item.

You can move the slide bar by selecting it with the mouse
cursor.  By holding the left mouse button down, you can
slide the bar back and forth.  The value of the bar at the
right is constantly updated.  The left and right arrows can
be used to fine tune the value of the slide bar.

*** Text Strings ***

Text strings are used to enter data which cannot be entered
by one of the previous methods.  This includes floating
point numbers and names.

Text strings are entered and edited with the keyboard.  A
text cursor appears at the location of the character which
is currently being edited.  The text cursor appears as a
single underscore and should not be confused with the mouse
cursor.

The Tab key moves the text cursor to the next string.  The
Backspace key deletes the previous character and move the
text cursor one character to the left.  The Escape key
deletes all characters on the current text line.

The text cursor can be quickly moved to any text string by
pointing to the new location with the mouse cursor and
clicking the left mouse button.

\Diffuse Reflection

The diffuse reflection coefficient governs the amount of
light a material reflects diffusely.  Diffuse reflection
depends only on the orientation of a surface with respect to
each light.  

The more a surface faces a light, the more light is
diffusely reflected and the brighter the surface will be.  

A dull mattte surface typically has a diffuse coefficient of
about 80 percent.  A mirror may have a diffuse coefficient
of only 10 percent.

\Directory Scroll Box

You can select a different current directory by using the
Directory scroll box.  The Directory box lists all
sub-directories of the current directory.  If there are too
many sub-directories to display at one time, use the scroll
bar to scroll through the directory list.

To change directories, move the cursor over the name of the
directory which you wish to make current and press the left
cursor button.  The Current File line and the File scroll
box will change to reflect the new current directory.

If the current directory is not the root directory, the
first item in the directory box will be two dots (..).  The
two dots represent the parent directory and can be used to
back up one directory level.

\Display Menu

The Display menu allows you to customize the appearance of
the screen. From the BIG D menu bar, select the Display drop
down menu.

The Display menu allows you to see all currently defined
views and lights, and to set various display options, screen
colors, and units.

\Display Options

Display Options allow you to control the way curved surfaces
are represented in the wire-frame views and set the size of
various icons used in the view ports.

\Distance Scaling Factor

The distance scaling factor controls how light diminishes as
it travels through space.  High distance scaling factors
cause light rays to diminish more than low distance scaling
factors.

In other words, objects far away from the light source are
darker than objects close.  Setting the Distance Scaling
Factor to zero causes light intensity to remain constant as
it travels - it does not reduce over distance.  

\Dithering

When a surface is rendered with BIG D, its intensity usually
changes from one location to another due to lighting and
view location.  Since rendering devices are limited to a
finite number of colors or intensity levels, it is sometimes
not possible to obtain a smooth gradation of intensity
change along the surface.

This limitation of the rendering device results in a banding
effect where the surface changes from one intensity level to
another.

Turning Dithering on helps eliminate this banding effect by
varying the intensity of each pixel by a random amount. This
random dithering smooths gradual changes in the intensity
level.

Dithering does not affect image generation time.

\Drive Scroll Box

The Drive scroll box lets you select a different disk drive
as the current drive.  To change drives, select a different
drive letter (if present) from the Drive scroll box.  

The Current File line, Directory box, and File box all
change to reflect the newly selected drive.

\Edit Current Command

The Edit External Command operation button allows you to
edit the currently selected external command.  Selecting
this button will cause the Edit External Command dialog box
to be displayed with the currently selected external
command.

The operation of the Edit External Command dialog box is
identical to the Add External Command dialog box.

\Editing an Existing Light

You can edit an existing light by selecting the Edit
Existing Light option from the Lights menu.  If only one
light currently exists, a dialog box for the light
immediately pops up, allowing you to edit its properties.

If more than one light currently exists, all lights are
drawn in the ports.  You can then select the light to edit
by positioning the cursor over its icon and pressing the
left mouse button.  The selected icon will become
highlighted as it is chosen.  Then select the OK button to
display the Edit Light dialog box for the selected light.

The Edit Light dialog box is identical to the Add Light
dialog box. You can use it to modify the light type,
location, hue, saturation, intensity and x-ray options.

\Editing an Existing View

You can edit an existing view by selecting the Edit Existing
View option from the Views menu.  If only one view currently
exists, a dialog box for the view immediately pops up,
allowing you to edit its properties.

If more than one view currently exists, all views are drawn
in the ports.  You can then select the view to edit by
positioning the cursor over either its target or camera icon
and pressing the left mouse button.  The selected icon will
become highlighted as it is chosen. Then select the OK
button to display the Edit View dialog box for the selected
view.

The Edit View dialog box is identical to the Add View dialog
box.  You can use it to modify the locations of the target
and camera, redefine the front clipping plane, or change the
number of generated views.

\Example of Angular Units

The example of angular units shows a sample of what the
current angular unit settings will produce.  The example
depends on both the current angular units and the current
angular precision. 

\Example of Linear Units

The example of linear units shows a sample of what the
current linear unit settings will produce.  The example
depends on both the current linear units and the current
linear precision.

\Execute Current Command

The Execute Current Command operation button permits you to
execute the currently selected external command.  When
selected, BIG D displays the Execute External Command dialog
box.

This dialog box shows the description of the external
command which is about to be executed.  It may also prompt
you for any command line arguments which may be needed.  If
command line arguments are needed, you can type these in
before executing the command.

Select the OK button to execute the external command or the
Cancel button to abort the command.  If you select OK, BIG D
will exit and run the command.  When the command terminates,
you will be asked to press a key to continue.  BIG D will
reload and you are free to continue working with the
currently open file.

NOTE: If the external command is a batch file, BIG D will
not reload when the command is finished.  Instead, control
is returned to the operating system.

\External Commands

The External Commands option allows you to run other
programs (such as AutoCAD) or DOS commands from within BIG
D.  When the external command is through, control
automatically returns to BIG D.  Selecting External Commands
from the File menu causes the External Commands dialog box
to appear.

The External Commands dialog box contains the current
command, a scroll box which contains a list of all available
commands, and four operation buttons which allow you to
execute, add, delete, and edit commands.

\External Command Operations

Four operation buttons are availble for accessing the
external command list.  The Execute Current Command button
allows you to execute the currently active external command.

The Add a New Command button lets you add a new command to
the external command list.  The Delete Current Command
button lets you delte the currently active external command.


The Edit Current Command button allows you to modify the
properties of the currently active external command.

\File Compression

The File Compression option tells BIG D whether to compress
the output image file as it writes it to disk.  BIG D uses
run length encoding to compress the image.  Resulting files
are typically 25 to 75 percent smaller than uncompressed
files.

If you are using BIG D generated file with other software,
you may need to turn File Compression off.  Some software
packages do not recognize compressed TARGA format files.

\File Format

Two output file formats are available.  The TGA option
creates Truevision TARGA format files.  This format was
originally developed for the TARGA series of graphics
adapters, but works equally well for 256 color images.

The PIX file format is a variation of the TARGA format and
should be used with the Vision 16 adapter from Vision
Technologies.  TGA image files are assigned .TGA extensions,
and PIX files have .PIX extensions.

\File Menu

The File menu on the BIG D menu bar offers various options
related to external files or programs.  These file commands
include opening and saving BIG D files, generating rendered
image files, displaying rendered image files, running
external programs or commands from within BIG D, saving the
current file, and quitting the BIG D program.

\File Scroll Box

All appropriate files which reside in the current directory
appear in the File scroll box.  If there are more files
available than will fit in the box at one time, you can use
the scroll bar to scroll through the file list.

To select a new current file, move the cursor over the name
of the file you wish to select and press the left mouse
button.  The name will highlight and the Current File line
above will change to show the new file name.

\File Type

File type refers to the extension of the file name you wish
to show. Current available options include TGA (which is the
standard TARGA format) and PIX (which is a variation of the
standard TARGA format used by Vision 16 based systems).

If you select TGA, only files with TGA extensions will
appear in the File scroll box.  If you select PIX, only file
with PIX extensions will appear in the File scroll box.

\Front Clipping Plane

The front clipping plane is an imaginary plane which is
perpendicular to the line of sight (the line from the camera
to the target).  BIG D ignores objects (or parts of objects)
which are on the camera side of the clipping plane.  

The distance to front clipping plane is measured from the
camera to the plane along the line of sight using the
current unit of measurement.  This distance is normally set
to zero, which locates the plane at the camera point.

Setting a non-zero distance to the front clipping plane
allows you to create cross-sectional views of your drawing.

\Generate Image

The Generate Image option of the File menu tells BIG D you
are ready to begin generating images.  Be sure you have
already set rendering options, assigned materials to the
layers of the drawing, and defined at least one light and
one view point.

Once you have selected the base output file name, the
rendering speed, and the generation mode, select the OK
button to begin the rendering. You can select the Cancel
button to abort the rendering.

If you have made any changes during this editing session,
BIG D will ask if you want to save them before generating
the rendering.  You will normally pick "Yes".

BIG D generates and saves each image in a TARGA file. If you
are generating 8-bit (256 color) images, BIG D introduces a
second phase to convert each image to 8 bits and optimize
the color map.

*** Aborting the Generation ***

To abort image generation after it has begun, press CTRL-Q
(press the CTRL key and the Q key at the same time).  BIG D
will display a warning box telling you that the generation
phase has been aborted. Select Continue to redisplay the BIG
D screen.

If you do not abort the generation phase, BIG D returns to
the BIG D screen as soon as it completes all images.  Each
image is now saved on disk as a TARGA file.

\Generated Frames

BIG D can generate up to 100 additional frames between each
defined view.  By using generated frames, you can easily
define a sequence of images for a walk-through animation.

A generated frame is simply a view which is automatically
created by BIG D.  Each frame has its own target and camera.

The cameras of the generated frames are equally spaced along
a straight line between the current camera and the next
camera. Similarly, the targets of the generated frames are
equally spaced along a straight line between the current
target and the next target.

If you give the last defined view a non-zero number of
generated frames, BIG D will generate the additional frames
between the last (current) view and the first defined view.

As an example, suppose you have defined three views and you
are editing view number 2.  You set the number of generated
frames for view number 2 to four. BIG D will generate four
additional frames between view number 2 and view number 3.

\Generation Mode

The generation mode option allows you to set the screen mode
which BIG D uses while it generates one or more images.
Three different modes selections are available: text,
graphics, and render.

If the text mode option is selected, BIG D will switch to
text mode before generating the image.  An on screen message
gives the status of the rendering (the percentage done) as
it is generated.  This option is useful is you are using a
multitasking operation system and wish to run BIG D in the
background while generating images.

The graphics mode option displays the status of the
rendering (the percentage done) in a message box.  You may
have to use this option if you are generating an image whose
resolution is greater than the rendering device can display.

The render mode option tells BIG D to display the image on
the rendering device as it is generated.  The image is
painted from the bottom up as it is generated.  

NOTE: This option is only available if the horizontal and
vertical resolution of the image is compatible with the
rendering device.

\Grid Size

Grid Size influences the level of precision with which BIG D
analyzes the 3D model.  You may set grid size at five
possible settings: 1, 2, 4, 8, or 16.  Lower numbers
increase accuracy but require more generation time.  Larger
numbers decrease accuracy but speed things up.  

When generating an image, BIG D does not determine the
intensity of every pixel in the image.  Instead, it divides
the screen into a grid and calculates the intensity of the
pixels at each grid intersection. The Grid Size option sets
the level of precision for the grid.

Once the grid size is known, BIG D analyzes each square
individually. If the corners of a square have the same
intensity, all pixels in that square are set to an identical
intensity.

If the intensities at the corners are different, BIG D
divides the square into four smaller squares.  The intensity
at the corners of each smaller square is calculated and each
smaller square is treated in the same manner as the initial
square.

The process repeats until every pixel in the initial square
is either filled in or calculated.  This method  saves
significant processing time, especially for large areas of
constant intensity.

Theoretically, the larger the grid size, the faster the
image is generated.  The only drawback of setting a large
grid size is that very small objects, thin horizontal or
vertical elements, or objects with sharp corners may be
missed by the grid.  If you find such areas incorrectly
rendered, you should reduce the grid size.

\Hour and Minute

The hour and minute of the day sets the exact position of
the sun. When setting the hour, be sure to specify either AM
for morning or PM for afternoon.

The hour and minute are based on true solar time.  That is,
the sun's bearing will be due south (in the northern
hemisphere) at exactly 12 noon.  Keep in mind that local
time will usually vary somewhat from true solar time.

\Hue

The hue is the name by which the color is defined, such as
red, yellow or violet.  For our purposes, the hue is defined
by an angle from 0 to 360 on a color wheel.  Red is located
at zero degrees, green is located at 120 degrees, blue is
located at 240 degrees, and so forth. But you do not need to
know which angle corresponds to which hue.  The color
selection screen handles that automatically.

\Inserting a New View

The Insert View option of the Views menu is similar to the
Add View option except that it allows you to insert a view
in the middle rather than the end of the view list.

Selecting the Insert View option displays the Plan and
Elevation ports with all currently defined views shown.  The
prompt strip at bottom of the screen asks you to "Select
view to follow new view...".

Select the view which is to follow the new view.  The
selected view will be highlighted.  Then select the OK
button to insert the new view.

The new view will be given the number of the view you just
selected. All views which follow the new view will have
their view number incremented by one.

The Add View dialog box appears for the new view.  You can
locate the new view's target and camera in the same manner
as you would when adding a new view to the end of the list. 

\Intensity

Intensity sets the brightness of the color.  For materials,
intensity is measured as a percentage.  An intensity of 90
percent will result in a very bright material.  A dark
material may have an intensity of only 30 percent.

For lights, intensity is measured as an absolute number.
Typical light intensities range from 2 for a weak light to
about 20 for a very bright light.  Intensity must be set
with a slide bar; the color selection screen does not set
intensity.

\Latitude

The latitude defines your location on earth relative to the
equator. It is measured as an angle from -90 degrees to +90
degrees.

A positive latitude (0 to +90 degrees) is used in the
northern hemisphere and a negative latitude (0 to -90
degrees) is used in the southern hemisphere.

\Layer Operations

The Layers dialog box contains two operation buttons: Assign
Material to Current Layer and Change Status of Current
Layer.

*** Assign Material to Current Layer ***

To assign a different material to the current layer, select
the "Assign Material to Current Layer" button.  The Layers
dialog box disappears and is replaced by the Assign Material
dialog box.

The Assign Material dialog box displays the name of the
current layer in the title.  Below the title is the name of
the material which is currently assigned to the layer.

Below the current material line is the materials scroll box.
The materials scroll box contains a list of the names of all
materials which are in the materials library.  The name of
the currently assigned material is highlighted in the scroll
box.

To select a different material, scroll through the list of
materials until the material appears in the box.  Move the
cursor to the line the material name is on and press the
left mouse button.

The material selected will highlight and the current
material above will change to the newly selected material.

Select the OK button to confirm the new material assignment.
The Assign Material dialog box will disappear and the Layers
box will reappear.  The newly selected material will now
show up on the current layer line.

Selecting the CANCEL button in the Assign Material dialog
box will discard any changes and return to the Layers dialog
box.

*** Change Status of Current Layer ***

BIG D maintains the on/off status of each layer in the
AutoCAD drawing.  Entities on layers which are turned off do
not appear in the view ports and are not rendered by BIG D.

Each layer's status is initially taken from the DXF file.
Layers which are turned off or frozen in the DXF file will
be turned off in BIG D.  All other layers are turned on.

To change a layer's status, select the desired layer so that
it is the current layer.  Then select the "Change Status of
Current Layer" button.  If the current layer's status was
on, it will be toggled to off.  If it was off, it will be
turned on.

The change in layer status will not take effect until you
select the Done button to exit the Layers dialog box.  If
any layer's status has changed, BIG D will regenerate each
view port to reflect the change.

\Layer Scroll Box

Before you can assign a material to a particular layer you
must select that layer as the current layer.  To select a
current layer, scroll through the list of layers (they are
in alphabetical order) until the layer you want is visible
in the scroll box.

Now move the cursor inside the scroll box to the line on
which the layer is located and press the left mouse button.
The entire line will highlight and the "Current Layer" above
the scroll box will change to the new layer name.

\Layers

The Layers option of the Materials menu allows you to
control the status of the layers in your AutoCAD drawing. In
AutoCAD, every entity is drawn on a layer.  All entities
which are drawn on the same layer are assigned the same
material properties.

Selecting the Layers option from the Materials menu will
activate the Layers dialog box.  At the top of the box just
under the box title is the name of the current layer.  The
current layer is the layer which is currently active.  It is
not necessarily the layer that was current in the AutoCAD
drawing.

Below the current layer line is a scroll box with a list of
the drawing's layers, the material assigned to each, and the
status of the layer (On or Off).  The current layer is
highlighted in reverse video in the scroll box.

Near the bottom of the dialog box are two operation buttons.
The "Assign Material to Current Layer" button lets you
assign a material from the material library to the current
layer.  The "Change Status of Current Material" button
allows you to toggle the current materials status from on to
off, or from off to on.

The first time you load a DXF file, BIG D automatically
assigns default materials from the library to each layer in
the drawing. Default materials are based on one of the first
eight colors available in AutoCAD (numbers 0 thru 7). For
example, layers using color 1 are initially assigned the
material RED.  

\Lens Focal Length

The Lens Focal Length determines the type of lens used for
all Camera views.  The focal length controls the width of
the viewing angle. Smaller focal lengths create wider
viewing angles.

Focal lengths are measured in millimeters and range from
15mm (a very wide angle lens) to 1000mm (a telescopic lens).
The default lens is a 35mm lens, which is the standard lens
used on most 35mm cameras.

Using different focal lengths for views of your 3D model
(say a 35mm study and a 15mm close-up study) requires
creating a separate file for each study.

\Light Hue

A light's hue is the color of the light.  It is defined as
an angle between 0 and 360 degrees.  The angle corresponds
to a color on a color wheel, with red at 0 degrees, green at
120 degrees, and blue at 240 degrees.

You can select a light's hue by picking an angle on the hue
slide bar or by using the color selection screen (see Select
Color).

\Light Icon Size

The Light Icon Size option sets the size of the light icons
which are drawn in the view ports to represent the location
of lights.  A point light icon is drawn as a circle
enclosing the light number with lines out from the circle. A
directional light icon is drawn as a circle enclosing the
light number with a set of parallel lines pointing in the
direction of the light.

The size of the light icon is measured in pixels.

\Light Intensity

A light's intensity is a measure of the brightness of the
light.  It is an absolute number (not a percentage) from 0
to 100.  The higher the number, the brighter the light.

Typical light intensity values range from 5 to 10.  As more
lights are added to a scene, the intensity of each light
must be lowered to keep the scene from becoming too bright.

You can select the light's intensity by using the slide bar
in the dialog box.

\Light Location

The location of a light depends of the light type.  If the
light is a point light, the light is located by its x, y, 
and z coordinates.

If the light is a directional light, the light is located by 
two angles.  The first angle is a bearing angle in the x-y
plane measured counter-clockwise from the x axis.  The 
second angle is an altitude angle measured in a vertical 
plane counter-clockwise from the x-y plane.

\Light Meter

The light meter allows you to quickly and accurately check
the current lighting level at any point in the scene.  You
can check the light meter by selecting the Light Meter
option from the Lights menu.

The light meter is an imaginary sphere which you can
position anywhere in the model.  The Light Meter dialog box
allows you to locate the sphere in the plan and elevation
ports and set its diameter.  You can choose a color for the
sphere and select a currently defined view from which to
view the meter.

The light meter sphere is assumed to have an ambient
reflection coefficient of 20 percent, a diffuse reflection
coefficient of 80 percent, and specular and transmission
coefficents of zero.

When you ask BIG D to show the light meter, the program
generates an actual ray-traced rendering of the sphere on
the rendering device. The sphere is viewed from a defined
view point and all currently defined lights are included in
the calculations.

\Light Meter Diameter

The light meter diameter is the diameter (in real units) of
the sphere which is to be rendered.  It is important that
you enter a diameter which is relative to the scale of your
drawing.  For example, if your model is 300 feet long and
you enter 1 inch for the light meter diameter, you will
probably see nothing when you ask BIG D to show the meter.

\Light Meter Hue

The light meter's hue is the color of the meter.  It is
defined as an angle between 0 and 360 degrees.  The angle
corresponds to a color on a color wheel, with red at 0
degrees, green at 120 degrees, and blue at 240 degrees.

You can select the light meter's hue by picking an angle on
the hue slide bar or by using the color selection screen
(see Select Color).

\Light Meter Location

The light meter is located by its x, y, and z coordinates.
You may type in the coordinates directly in the dialog box
or use the Locate operation button to graphically locate the
light meter.

\Light Meter Operations

The Light Meter dialob box offers four operation buttons:
Locate, Select Color, Select View, and Show Meter.

*** Locate ***

The Locate operation button allows you to graphically locate
the light meter in the plan and elevation view ports.
Selecting the Locate button removes the dialog box and draws
an icon representing the light meter in both the Plan and
Elevation ports.

The light meter icon is a circle with a capital M inside.
The Plan port locates the x-y coordintates of the light, and
the Elevation port locates the z coordinate of the light.

You may relocate the icon by moving the small black
rectangular cursor over the light meter icon and clicking
the left mouse button.  The box cursor turns into
cross-hair.  

Move the cross-hair to the new location (a rubber band
connects the cross-hair with the old location).  When you
reach the new location, click the left mouse key to relocate
the icon.

When you have correctly located the light meter, select the
OK button in the prompt area to return to the light dialog
box.

*** Select Color ***

The Select Color operation button allows you to pick the
color (hue and saturation) of the light meter using the
color selection screen on the rendering device.  Changes
made in the color selection screen will be reflected in the
hue and saturation slide bars.

Refer to Select Color for more information on the operation
of the color selection screen.

*** Select View ***

You can select the any currently defined view from which to
display the light meter.  If only one view is defined, that
view (view number one) must be used and the Select View
button is disabled.

If more than one view currently exists, picking the Select
View button will cause the Light Meter dialog box to
disappear and all views to be drawn in the ports.  

You can then select a view by positioning the cursor over
either its target or camera icon and pressing the left mouse
button.  The selected icon will become highlighted as it is
chosen.  Then select the OK button to redisplay the Light
Meter dialog box.

The View Number line in the Light Meter dialog box will
reflect the new view chosen.

*** Show Meter ***

Once you have the light meter parameters set, select the
Show Meter button. BIG D generates a ray traced image of the
sphere on the rendering device.  The image is viewed from
the currently selected view number and takes into account
all currently defined lights.

You can observe the rendered sphere to determine if the
current lighting levels are too high or too low.  Hit any
mouse button to return to the Light Meter dialog box.

You can adjust the intensities or location of lights, then
use the light meter to re-check lighting levels. 

\Light Meter Saturation

Saturation is the purity or vividness of the color, measured
as a value between 0 and 100 percent.  A pure color is 100%
saturated.  As white is added, saturation decreases.  Zero
saturation gives no color at all, a shade of gray.  

You can select the light meter's saturation by picking a
percentage on the saturation slide bar or by using the color
selection screen (see Select Color).

\Light Meter View Number

The light meter view number is the currently selected view
from which you wish to see the light meter.  You can select
any currently defined view point by using the Select View
operation button.

\Light Operations

The light dialog box has two operation buttons: the Locate
button and the Select Color button.

*** Locate ***

The Locate operation button allows you to graphically locate
a light in the plan and elevation view ports.  Selecting the
Locate button removes the dialog box and draws icons
representing the current light in both the Plan and
Elevation ports.

Point lights icons are small circles with little light rays
radiating in all directions.  The Plan port locates the x-y
coordintates of the light, and the Elevation port locates
the z coordinate of the light.

Directional light icons are small circles with little
parallel rays pointing toward the center of the port.  The
plan port determines the horizontal orientation of the
light.  

The horizontal angle can be from 0 to 360 degrees (0 is
parallel to the x-axis). The Elevation port sets the
vertical angle from which the light is coming.  The vertical
angle ranges from -90 to +90 degrees.  

You may relocate the icons by moving the pick box cursor
over the light icon and clicking the left mouse button.  The
box cursor turns into cross-hair.  

Move the cross-hair to the new location (the cross-hair
remains tethered to the old location).  When you reach the
new location, click the left mouse key to relocate the icon.

NOTE: When locating directional lights, remember that you
are specifying angles and not absolute coordinates.  The
directional light icons are relative only to the center of
the view port and have no relationship to the model itself.

When you have correctly located the light, select the OK
button in the prompt area.  The Light dialog box reappears
with the new light location.

*** Select Color ***

The Select Color operation button allows you to pick the
color (hue and saturation) of the light using the color
selection screen on the rendering device.  Changes made in
the color selection screen will be reflected in the hue and
saturation slide bars.

Refer to Select Color for more information on the operation
of the color selection screen.

When finished with the Lights dialog box, select OK to add
the new light to the light list or select Cancel to abort.
Either choice exits the Light dialog box.

\Light Saturation

Saturation is the purity or vividness of the color, measured
as a value between 0 and 100 percent.  A pure color is 100%
saturated.  As white is added, saturation decreases.  Zero
saturation gives no color at all, a shade of gray.  

You can select a light's saturation by picking a percentage
on the saturation slide bar or by using the color selection
screen (see Select Color).

\Light Type

Two types of lights are available in BIG D: point lights and
directional lights.  

A point light is located at an infinitely small point in 3D
space, defined by its x, y, and z coordinates.  A point
light radiates light rays in all directions equally.

If the distance scaling factor is non-zero (see rendering
options), the intensity of the light dimishes as it travels
throught space. Light bulbs are examples of point lights.

If you select the point light type, BIG D requests that you
enter the location of the light with its x, y, and z
coordinates.  You can also locate the light graphically in
the view ports by selecting the Locate button near the
bottom of the dialog box.

A directional light is a light which is located at an
infinite distance from the scene.  A directional light emits
rays which are parallel to each other.

The direction from which the light rays originate is defined
by two angles: a horizontal angle and a vertical angle.  The
horizontal angle is measured in the x-y plane
counter-clockwise from the x-axis.  The vertical angle is
measured counter-clockwise from the x-y plane.

The intensity of a directional light does not diminish as it
travels through space.  Therefore, directional lights
generally appear brighter than point lights of equal
intensity.

You may locate a directional light by typing the angles or
by selecting the Locate button to visually position the
light in the view ports.

\Lights Menu

BIG D offers several different types of lights which you can
use to realistically illuminate your model.  The types of
lights include point lights, directional lights, sun light,
ambient light, and special x-ray lights.  

BIG D allows you to define any number of point and
directional lights. The program maintains a list of defined
lights.  You must always define at least one light in order
to generate an image.

You may add new lights, and delete or edit existing lights.
You can position each light in the view ports and set each
light's color and intensity.

A light meter is available to help you check lighting levels
at any location in the model before generating an image.

All lighting controls can be accessed through the Lights
menu.  The Lights menu has six options:  add a new light,
delete an existing light, edit an existing light, the
ambient light, the sun, and the light meter.

If no lights are currently defined in the scene, the Delete
a Light and Edit a Light options are disabled.

\Linear Precision

Linear precision sets the precision with which linear
coordinates and measurements are displayed.  For scientific,
decimal, and engineering units, this is the number of
decimal places displayed.  For architectural and fractional
units, this sets the fractional accuracy which is displayed.

\Linear Units

Linear units are used to display all coordinates and
distances. Select your preference of scientific, decimal,
engineering, architecural, or fractional units.

\Locating Target and Camera

When you select the Locate button BIG D removes the dialog
box and draws icons representing the current camera and
target in both the plan and elevation ports.  A message in
the prompt area asks you to "Select TARGET or CAMERA...".

*** Camera and Target Icons ***

The camera icon is a small square with a view number inside.
The target icon is a square with an X inside.  The camera
icon is connected to its corresponding target by an arrow
which points toward the target.

The plan port displays the the x-y coordinates of the camera
and target, and the elevation port displays the z elevations
of the camera and target.

If either camera or target icon cannot be seen, you may need
to zoom out of the port.  Use the zoom out button in the
upper right corner of each port to back up until you can see
each icon.

*** The Pick Box ***

Moving the cursor into the plan or elevation port causes it
change into a pick box.  The pick box is used to select
either the camera or target icon.

*** Moving the Icons ***

To move an icon, you must first select it.  Place the pick
box over the icon and press the left mouse button.  The pick
box turns into a small cross.  The cross is connected to the
remaining icon by a rubber band.

To complete the move, drag the icon to its new location and
press the left mouse button.  The selected icon is redrawn
at the new location and the cross cursor again becomes a
pick box.

After locating the camera and the target icons in both the
plan and elevation ports, select the OK button in the prompt
area (or Cancel to abort) to return to the Add View dialog
box.  The coordinates of the target and camera in the dialog
box will now reflect the new locations of the target and
camera.

\Map Width and Map Height

The map width and height control the scale of the texture
map.  It is important that you supply reasonable values for
the map width and height.

The width of the map is the horizontal width of the file
image in real world units.  The height of the map is the
vertical size of the image in real world units.

If a textured object appears to be incorrectly textured, it
is probably because the map width and height are not set
properly.

The lower left corner of the texture map is considered the
origin. The origin of the texture map will correspond to the
local origin of the entities to which the texture is mapped.


For example, if a texture is mapped to a circle whose center
is located at 0,0 (in the circle's UCS), the lower left
corner of the texture will be mapped to the center of the
circle.

\Material Hue

A material's hue is the color of the material.  It is
defined as an angle between 0 and 360 degrees.  The angle
corresponds to a color on a color wheel, with red at 0
degrees, green at 120 degrees, and blue at 240 degrees.

You can select a material's hue by picking an angle on the
hue slide bar or by using the color selection screen (see
Select Color).

\Material Operations

The Materials dialog box offers four operation buttons: Add
a New Material, Delete Current Material, Edit Current
Material Properties, and Edit Current Material Texture.

*** Add a New Material ***

This operation lets you add a new material to the material
library.

*** Delete Current Material ***

You can delete the currently selected material from the
material library by selecting the "Delete Current Material"
operation button. BIG D will ask you to confirm the material
deletion.  You can select the OK button to delete the
current material or select the CANCEL button to retain the
material.

*** Edit Current Material Properties ***

The Edit Current Material Properties operation button allows
you to edit the surface characteristics of the current
material.  Select the Edit Properites button to display the
Edit Material Properties dialog box.

*** Edit Current Material Texture ***

This operation lets you assign or modify the texture map
which is associated with the currently active material.

\Material Properties

The Edit Material Properties dialog box displays the current
values of the material's properties.  Material properties
include hue, saturation, ambient reflection coefficient,
diffuse reflection coefficient, specular reflection
coefficient, transmission coefficient, specular exponent,
refraction index, and the reflection mapping option.

\Material Properties Operations

Two operation buttons are available.  The "Select Color"
button lets you select the surface hue and saturation on the
rendering device.  The "Show Properties" button displays a
crude representation of the material on the rendering
device.

*** Select Color ***

The Select Color operation button allows you to pick the
color (hue and saturation) of the material using the color
selection screen on the rendering device.  Changes made in
the color selection screen will be reflected in the hue and
saturation slide bars.

Refer to Select Color for more information on the operation
of the color selection screen.

*** Show Properties ***

The Show Properties operation button will display a sphere
with a rough approximation of the current material's
properties on the rendering device.

When displaying the sphere, Show Properties considers only
the material's hue, saturation, ambient reflection
coeffiecient, diffuse reflection coefficient, and specular
reflection coefficient.  Show Properties does not take into
account the material's transmission coefficient, specular
exponent, refraction index, or texture map.

Click any mouse key to exit the sphere display and return
the Properties dialog box.  

When finished with the Properties dialog box, select OK to
save your changes (or select Cancel to abort).  Either
choice returns you to the main Edit Materials dialog box.

\Material Saturation

Saturation is the purity or vividness of the color, measured
as a percentage.  A pure color is 100 percent saturated.  As
white is added, saturation decreases. Zero saturation
results no color at all, a shade of gray.  

You can select a material's saturation by picking a
percentage on the saturation slide bar or by using the color
selection screen (see Select Color).

\Materials

BIG D maintains a library of materials which you can assign
to layers. If the exact material you need is not already in
the library, you can easily add a new material to the
library.

You can also modify existing materials in the library and
delete existing materials from the library.

The Materials option of the Materials menu allows you to
modify the materials library.  Selecting Materials activates
the Materials dialog box.

The Materials dialog box displays the currently active
material just under the box title.  Below this is a scroll
box which contains an alphabetic list of the names of all
materials which are in the library.

Below the scroll box are four operation buttons used to
modify the materials library.

\Materials Menu

BIG D maintains a library of materials which you can assign
to the layers of your AutoCAD drawing.  The Materials menu
allows you to assign materials to layers, control which
layers are rendered, modify or delete existing materials in
the library, and add new materials to the library.

\Materials Scroll Box

Before you can modify a material you must select that
material as the current material.  To select a new current
material, scroll through the list of materials until the
material you want is visible in the scroll box.

Move the cursor inside the scroll box to the line on which
the material is located and press the left mouse button. The
entire line will highlight and the current material above
the scroll box will change to the new material name.

\Menu Colors

The menu colors set the colors used to draw the menu bar and
drop down menus.  The halftone color is used to draw menu
options which are disabled.

\Menus

Drop down menus appear when you move the cursor over the
menu headings on the menu bar.  Each menu contains several
related options.

You can select a menu option by dragging the cursor downward
through the menu until it is located over the option you
want.  Then click the left mouse button.

As you move the cursor up or down the menu, each selectable
menu option is highlighted in reverse video. Non-highlighted
options are disabled and cannot be selected.

Most menu options have keyboard shortcuts, designated by an
underlined letter in the menu option.  You may type the
letter to access the command without using the mouse.

For example, to open a new file using keyboard shortcuts,
first press F to display the File Menu.  Then press O to
access the Open File dialog box.  BIG D erases the File Menu
and displays the Open File dialog box just as if you had
used the mouse cursor for your selections.

\Month and Day

The month of the year and day of the month specified to tell
BIG D the time of the year you want to see the sun.  BIG D
uses this information to determine the tilt of the earth
relative to the sun.

\Mouse

The mouse is a pointing device which controls the screen
cursor.  The cursor is normally shaped like an arrow, but
sometimes turns into a cross or box.

Use the left mouse button to select items from the screen.
When prompted to select an item from the screen, move the
cursor over the item and press the left button ("click on"
the item).

Clicking the right mouse button is equivalent to hitting
Return (or Enter) on the keyboard.  The middle button (if
available) is the same as selecting the Cancel button in
dialog boxes.

The keyboard cursor keys can now be used to move the mouse
cursor.  A mouse is no longer required to use BIG D,
although a mouse is strongly recommended.

The functions of the keys which move the cursor are
summerized as follows:

  KEY          FUNCTION
  Up Arrow     Moves the cursor up.
  Down Arrow   Moves the cursor down.
  Left Arrow   Moves the cursor to the left.
  Right Arrow  Moves the cursor to the right.
  Home         Moves the cursor up and to the left.
  Page Up      Moves the cursor up and to the right.
  End          Moves the cursor down and to the left.
  Page Down    Moves the cursor down and to the right.
  Insert       Same as pressing the left mouse button.
  Delete       Same as pressing the right mouse button.

Initially, each cursor key moves the cursor one pixel in the
appropriate direction.  The F9 and F10 function keys can be
used to adjust the distance the cursor moves with each key
press.

Each time you press the F10 key, the amount of cursor
movement doubles. Each time you press the F9 key, the amount
of cursor movement is cut in half.  If the current cursor
movement is one pixel, the F9 key has no effect.

\New Material Name

At the top of the Add a Material dialog box is a prompt for
the new material name.  You can type in a descriptive name
for the new material up to 15 characters.

\North Angle

The north angle is a horizontal angle which points toward
true north. The angle is measured in the x-y plane
counter-clockwise from the x-axis.

For example, if true north is in the positive Y direction,
the north angle will be 90 degrees.  BIG D adjusts the
bearing of the sun for the north angle.

\Open File

The Open File option of the File menu lets you open and load
an existing AutoCAD DXF file.  Select Open File to display
the OPEN FILE dialog box.

Highlight the DXF file you wish to open using the drive,
directory, and file scroll boxes.

Select the OK button to begin loading the new DXF file.  The
screen will clear and BIG D will begin reading the DXF file
and converting it into a more efficient format.

BIG D creates several files from the DXF file, but the only
one you need to know about is the BDX file.  The BDX file
has the same name as the DXF file, but with a BDX extension
in place of the DXF extension.

The BDX file contains all the information BIG D needs to
know about the model including the model geometry, rendering
options, lighting information, view point locations, and
material assignments. Therefore, you should be careful to
never delete your BDX file or you will lose this
information.

BIG D also creates several other files with similar
extensions (BDW, BD0, BD1, and BD2).  These files are not
required by BIG D, but if they already exist BIG D will load
much faster.

NOTE: If you find you are running out of disk space, you can
regain some by deleting BIG D's temporary files.  A utility
batch file called BDCLEAN is available for cleaning out any
non-critical BIG D data files.  To delete non-crictical
files from the DOS prompt, type "BDCLEAN" and the file name
(without any extension) to be cleaned. For example, to
delete all temporary data files created by BIG D for the
SAMPLE drawing, type "BDCLEAN SAMPLE".

When BIG D finishes converting the DXF file, it will redraw
the entire screen.  The title bar at the top of the screen
will show the new current file name.  The plan and elevation
ports will be drawn with wire-frame views of the model.

NOTE: You can open and load a DXF file from the BIG D
command line by simply adding the new file name (without the
DXF extension) to the "BIGD" command.  For example, to load
SAMPLE.DXF into BIG D at the DOS prompt, type "BIGD SAMPLE".
Be sure to separate "BIGD" and "SAMPLE" with a space.

\Options Menu

BIG D can create several types of renderings.  General
parameters which control the type and quality of the
generated image are grouped under the Options menu.

The Options menu offers three selections: rendering options,
rendering file, and background color.

\Pick Cursor Size

The Pick Cursor Size option sets the size of the pick cursor
displayed when picking cameras, targets, and lights in the
view ports.  The pick cursor is drawn as a small box or
square.  The size is measured in pixels.

\Port Colors

The port colors set the colors used to draw the border
elements of the view ports.  This includes the title bar at
the top of each view port, and the scroll bars at the left
and bottom of each view port.

Changes in the Select Color dialog box do not take effect
until you select the OK button.  The entire screen will be
redrawn using the newly selected colors.  The Cancel button
can be used to discard color changes.

\Ports

Ports display wire-frame views of the AutoCAD 3D model and
allow you to easily locate functional items such as "Views"
and "Lights" anywhere in the model.  The left port displays
a plan view of the model and the right port displays an
elevation view.

Each port is made up of four elements: the title bar along
the top of the port, the horizontal scroll bar at the
bottom, the vertical scroll bar along the right side, and
the drawing area which fills in the rest of the port.

*** Port Title Bar ***

The title bar consists of the title of the port ("Plan" or
"Elevation"), a zoom-in button, and a zoom-out button.  

*** Zoom-In ***

The zoom-in button is located at the left end of the title
bar and is marked by two inward pointing arrows.  Clicking
on the zoom-in button causes the port to zoom inward in
small increments, making the drawing appear to grow larger.

*** Zoom-Out ***

The zoom-out button is at the right end of the title bar,
marked by two outward pointing arrows.  The zoom-out button
is the compliment of the zoom-in button.  It causes the port
to zoom outward in small increments, making the drawing
shrink.

*** Enlarging Ports ***

Between the zoom-in and zoom-out buttons is the title area.
Clicking on the title area over the "Plan" port causes the
"Plan" port to fill almost the entire screen, covering the
other port.

Similarly, clicking on the title area over "Elevation"
causes it to fill almost the entire screen, covering the
Plan port.  Clicking on the title area again causes the port
to return to its original size and the other port to be
redrawn.

*** Horizontal Scroll Bar ***

The horizontal scroll bar runs along the bottom of the port.
It allows you to pan the drawing to the left or to the
right.

Selecting the left arrow (at the left end of the scroll bar)
will cause the port to scroll a small amount to the left.
This makes the drawing jump a little to the right.  The
right arrow makes the port move a little to the right.

Between the arrow buttons is the scroll bar area.  The
scroll bar area shows you approximately where you are
located horizontally in the drawing.  As you pick the left
arrow, the scroll bar moves left to reflect the change.

The scroll bar itself can be selected to move quickly left
or right. The scroll bar itself will become centered at the
location you pick.

*** Vertical Scroll Bar ***

The vertical scroll bar is located along the right side of
the port. It controls the vertical location of the port in
the drawing and its operation is similar to that of the
horizontal scroll bar.

The small blank box at the lower right corner of each port
is the redraw box.  Selecting it redraws the entire port
without changing any of the viewing parameters.

*** Additional Notes ***

The port drawing area is used to locate and move items such
as views and lights.  Normally, picking the drawing area has
no effect on the port.

Whenever you zoom or scroll a port, BIG D must redraw the
entire port. This is similar to a redraw in AutoCAD.  For
very large drawings, the redraw time may take several
seconds.

Fortunately, you can cancel the redraw at any time by
pressing the left mouse button.  This allows you to move
around much more quickly.

For example, you can quickly zoom in on a drawing by
clicking the zoom-in button several times in a row.  One
more click will redraw the port at the new location.

\Procedure

Here is a summary of the steps you should take to quickly
get up and running with BIG D.  

Step 1. Build the Model

Before you can render with BIG D, you must have a 3D model
(in DXF format) to render.  The Using AutoCAD chapter offers
tips for building 3D models and instructions on how to
create the DXF file.

A sample DXF file (named SAMPLE.DXF) is supplied with BIG D
for your use.  It is located in the BIG D directory.  We
suggest you use this simple model to become familiar with
BIG D.

Step 2. Load BIG D

If you are inside the AutoCAD drawing editor, you must exit
AutoCAD before you can run BIG D.  To load BIG D, type
"BIGD" at the DOS command prompt.

Before continuing, you may want to browse throught the
chapter named Interface Overview.  This chapter gives you a
general overview of BIG D's graphical user interface and how
each element works.

Step 3. Open the DXF File

Once BIG D is loaded, you can open the DXF file by using the
Open File command of the File Menu.  See the File Menu
chapter for detailed instructions on opening a DXF file.

Step 4. Set Options

The Options Menu allows you to set various parameters which
control the appearance and format of the output image.  

You should pay particular attention to the Rendering File
dialog box. It controls the format of the output image file.
Bits per Pixel, Horizontal Resolution, and Vertical
Resolution are three items which must be set correctly to
obtain the best results.  See the Options Menu chapter for
details.

Step 5. Locate Lights

You must define at least one light source.  Use the Add a
Light command of the Lights Menu to add a light source to
the scene.  The Add Light dialog box lets to locate the
light in the plan and elevation ports.  The Lights Menu
chapter explains the procedure.

Step 6. Define Views

You must also define at least one view.  A view consists of
a camera and a target.  Together they determine how you will
see the model in the generated image.

Use the Add a View command of the Views Menu to add a view
to the scene.  In the Add View dialog box, use the Locate
operation to locate the camera and target in the plan and
elevation ports.

Return to the dialog box and use the Wire-Frame operation to
fine tune the locations of the camera and target to get
exactly the view you want.  Refer to the View Menu chapter
for instructions.

Step 7. Assign Materials

Materials are assigned to objects in the model by layer.
Each layer in the model is automatically assigned a material
from the materials library when you first open the DXF file.

You can change the materials assignments by using the Layers
command of the Materials Menu.  This allows you to assign
any material to any layer.  See the Materials Menu chapter
for details.

Step 8. Generate the Image

Now you are ready to generate the rendered image.  Use the
Generate Image command of the File Menu.  The image
generation phase can be time consuming, so you may wish to
use a rendering speed of 2 or 4.

BIG D will display a rough approximation of the image as it
is rendered.  The final image is saved to the hard disk in
an image file.

Step 9. Show the Image

When the generation phase is complete, you can view the
finished image with the Show Image command of the File Menu.
Show Image displays the final rendering on your rendering
device.  See the File Menu chapter for details.

Step 10. Making Changes

You can change any rendering attributes in BIG D and
generate additional renderings.  For example, to change the
view use the Edit a View command of the Views Menu.  Or you
can assign different materials to the model using the Layers
command of the Materials Menu.

If you want to make a change in the model itself (such a
moving a chair to the other side of a room) you must make
the change in AutoCAD, then reload the updated DXF file into
BIG D.

BIG D remembers all rendering options, lights, views, and
material assignments from the last session, so you do not
have to reenter any information.  You do have to generate a
new image in order to see the effects of the changes you
have made.

\Projection Type

This setting governs the type of projection method used to
generate the image.  You may select either parallel or
perspective.  

In a parallel projection, edges which are parallel in the
AutoCAD 3D model are parallel in the generated view.
Parallel projections include plans, elevations, and
isometric views.

A perspective projection gives a more realistic
representation of the 3D model.  Edges parallel in the
AutoCAD 3D model converge toward "vanishing points" in
perspective.

\Prompts

BIG D allows you to add up to three command line arguments
to each external command.  A command line argument is simply
an extra word or option which is added to the command line
before execution.

The Prompt lines let you fill in prompts for the command
line arguments.  These prompts will be displayed later when
you execute the external command.  The Prompt lines may be
left blank if no command line arguments are needed.

\Quit

You can exit BIG D by selecting the Quit option of the file
menu.

If you have made changes in the current editing session, BIG
D asks if you wish to save them before exiting.  Select Yes
to save the changes to the BDX file before quitting.  Select
No to quit without saving changes.

\Reflection Mapping

The reflection mapping option controls whether or not BIG D
calculates the reflection mapping of other objects in a
specularly reflective surface.

If reflection mapping is on and the specular reflection
coefficient is non-zero, BIG D will calculate the
reflections of other objects which can be seen in the
materials surface.

If reflection mapping is off, no reflection mapping
calculations will take place.  The material will still
appear shiny and show specular highlights without the
overhead of reflection mapping calculations.

If the global reflections options (see rendering options) is
set to off or the material's specular reflection coefficient
is zero, the reflection mapping option has no effect.

\Reflections

BIG D allows you to assign reflective materials to objects
in your model.  BIG D can calculate the reflected images of
other objects on the surface of objects with reflective
properties.  This process is called reflection mapping.

Reflection mapping can add substantially to the time
required to generate an image, especially if you have many
reflective surfaces. The Reflections option lets you turn
off reflection mapping calculations to speed image
generation.

With Reflections On, objects with reflective surfaces
reflect other objects in the model.  Enabling Reflections
can dramatically increase the realism of a scene.

On the other hand, you can turn Reflections Off to suppress
all calculations involving reflections.  Reflective objects
still appear shiny in the rendering, but they do not reflect
other objects.

\Refraction Index

The refraction index determines the amount that a light ray
is refracted or bent as it passes through a light
transmitting material. The higher the refraction index, the
less the light rays are refracted as they pass through a
light transmitting object.

A refraction index of 100 percent will allow light to pass
straight through the object with no refraction.  An index of
95 percent will produce slight refraction effects and result
in the distortion of objects which can be seen through the
light transmitting object.

A refraction index of 90 to 95 percent is typical for light
transmitting materials such as glass or water.  The
refraction index has no effect on materials with a zero
transmission coefficient.

Objects must contain a closed volume in order to refract
transmitted light.  Examples of objects which contain closed
volumes include closed extrusions made up of LINES and ARCS,
surfaces of revolution created by BDRSURF whose
cross-sections are a closed shape, and extruded SOLIDS.

Objects which are planar in nature will not refract
transmitted light. Planar objects include 3D FACES, 3D
MESHES, extrusions which do not form closed shapes, surfaces
of revolution created by BDRSURF whose cross-sections are
not closed shapes, and closed shapes with zero thickness.

\Relative Pixel Size

If the aspect ratio of your screen is not perfectly square,
you can use slide bars to adjust the Relative Pixel Width
and Height in the image file.  This keeps your rendered
images from being distorted when displayed on screen.

A good way to check "screen aspect" is to generate a
rendering of a circle and view it exactly perpendicular to
the plane of the circle so no distortion occurs.  Then
display the image and measure the actual width and height of
the circle on the screen.

If the width and height are identical, then there is no
need to adjust the relative pixel width and height. However,
if they are not the same, you should set the Relative Pixel
Width and Height to the same proportions as the width and
height of the circle.

For example, suppose your rendered circle measures 5.5
inches wide and 4.25 inches high.  To correct this
distortion, set the relative pixel width to 550 and the
relative pixel height to 425.  (The main consideration is
for the pixel settings to have the same proportions as the
display.)

\Rendering File

When BIG D generates an image, it saves the image in a disk
file.  The rendering file options let you set the properties
of this disk file.

Select the Rendering File item from the Options menu to
display the Rendering File dialog box.  The Rendering File
dialog box offers several settings for managing your image
output file: file format, antialiasing, dithering, file
compression, bits per pixel, horizontal and vertical
resolution, and image aspect ratio.

\Rendering Options

Rendering options control the type and quality of the
rendered image. Several rendering options are available.
Some options allow BIG D to generate images faster while
sacrificing some image quality.

Select Rendering Options from the Options menu to display
the Rendering Options dialog box.

The Rendering Options dialog box offers seven settings for
controlling how your object is rendered: projection type,
reflections, shadows, transmission, grid size, lens focal
length, and distance scaling factor.

\Rendering Speed

Generating a rendering with BIG D can require a substantial
amount of time.  The rendering speed option allows you to
generate renderings more quickly with some loss in image
resolution.  

The option numbers relate more to the resulting image
clarity than they do to the generation speed.  Option number
1 is the normal generation speed and will generate the
highest quality image.  Higher numbered options each
generate the rendering faster while losing some image
clarity.

This option lets you generate image "proofs" to check
lighting levels and material properties relatively quickly.
When you have all lights and materials set to your liking,
reset the rendering speed to 1 to generate the final
rendering(s).

NOTE: The rendering speed cannot be more than twice the grid
size.  If the "4" or "8" button is disabled, it is because
the grid size is not set high enough.  To use these higher
rendering speeds you must first increase the grid size
option in the Rendering Options dialog box (see the Options
menu).

\Repeat Mode

The repeat mode option allows you to repeat a texture map
infinitely in all directions.  Texture maps are finite in
size, but may need to cover surfaces which are larger than
the map itself.

The repeat mode tells BIG D to repeat a texture map in all
directions so that it will cover any size object.  Three
repeat mode options are available: off, normal, and reflect.

If repeat mode is off, BIG D will not repeat the texture
map.  Points on the object surface which are outside the
limits of the map (given by the map width and height) will
be assigned the material's default color.  The material's
color is assigned in the Edit Material Properties dialog
box.  This option can be used for textures which do not
repeat, such as a painting.

If the repeat option is set to normal, the texture map is
repeated infinitely in all directions.  This options works
well for regular textures in which the left and right edges
and the top and bottom edges of the texture match.

If the opposite edges of the texture map do not match, the
normal repeat mode will show seams at the edges of the map.
The reflect repeat mode can be used to eliminate the seams.

The reflect repeat mode option repeats the texture to
infinity, but also reflects the texture as it is repeated.
The option works well for irregular textures such as wood
grain or marble.

\Resolution

You may use slide bars to set the horizontal and vertical
(width and height) resolution of the output image.  Width
and height are measured in pixels.  

To set the resolution, locate the cursor near the middle of
the slide bar.  Press and hold down the left mouse button
and glide the mouse horizontally.  As the cursor pulls the
slide bar along  left or right, the number to the right end
of the slide bar changes.  

When you reach a number close to the one you need, release
the left mouse button.  Then fine tune by clicking the left
or right arrows to change the number by increments of one.
You should quickly obtain exactly the resolution you need.

NOTE: It is very important that you set the image resolution
correctly.  An incorrect setting may not allow you to
display the rendered image on your rendering device.

\Rotation Angle

The rotation angle allows you to rotate the texture map
before it is mapped to an object.  The angle of rotation is
measured in degrees in a counter-clockwise direction.

\Saturation

Saturation refers to the purity of the color.  It is
measured as a percentage.  Zero saturation gives no color at
all, a shade of grey. One-hundred percent saturation gives
pure color.  Again, the color selection screen handles the
selection of a saturation automatically.

\Save

The Save option of the File menu lets you save any changes
you have made in the current editing session.  All changes
are saved in the current BDX file.

When you select the Save option, BIG D asks to confirm your
selection. Select Yes to save changes to the BDX file or No
to cancel the Save option without saving changes.

NOTE: If no changes have been made in the current editing
session, the Save option of the File menu is disabled.

\Screen Colors

The Screen Colors option of the Display menu allows you to
select the colors used by BIG D to draw the components of
the screen.  

Each screen component has a foreground, a background, and a
halftone color.  The halftone color is typically used to
represent items which are disabled.

The current colors for each component are designated by
check marks in the appropriate color boxes.  To select a new
color, move the mouse cursor to a new color box and press
the left mouse button.  The check mark will move to the new
box.

\Screen Organization

The basic screen consists of a title bar, a menu bar, two
view ports, and a status bar.  The view ports are not
displayed until an AutoCAD DXF file is opened.  

The title bar, located at the top of the screen, displays
the program version number and the name of the currently
opened file.  Just below the title bar is the menu bar,
which provides access to the drop down menus.

The two ports display wire-frame views of the currently
opened DXF file.  The left port displays a plan view and the
right port displays an elevation view.

The prompt area is a screen-wide strip at the bottom which
sometimes queries for information when you are using the
ports.  It is usually blank.

\Select Color

BIG D allows you to attach colors to several objects:
lights, materials, and the screen background.  BIG D offers
a quick and easy method for selecting colors called the
color selection screen.  The color selection screen uses the
rendering device and the mouse to quickly select any
possible color.

A color consists of three components: hue, saturation, and
intensity. Any dialog box which needs a color will have
slide bars for hue and saturation.  A slide bar for
intensity may also be available.

Any dialog box which needs a color will have a Select Color
button in addition to the slide bars previously mentioned.
Choosing the Select Color button will transfer control to
the rendering screen.  The rendering screen will display a
color rectangle in the center of the screen, a horizontal
bar along the bottom of the screen, and a vertical bar along
the right edge of the screen.

The color rectangle in the center displays the currently
selected color.  The horizontal bar below is the hue bar.
The vertical bar to the right is the saturation bar. Markers
at the hue and saturation bars show the location of the
values which combine to create the current color.

To adjust the hue, move the mouse horizontally back and
forth.  The hue marker will move and the color rectangle
will change to reflect the changing hue.

To adjust the saturation, move the mouse up and down.  The
saturation marker will move and the color rectangle will
change to reflect the changing saturation.

With a little experimentation, you will be able to quickly
select the exact color you are looking for.  When you get
it, press either the left or right mouse buttons to confirm
your choice.  Control will return to the dialog box and the
values in the hue and saturation slide bars will reflect the
new color selection.

If you decide not to change the color after you have entered
the color selection screen, press the middle mouse button to
cancel the color selection and return to the dialog box.

If the color rectangle does not appear in the color
selection screen, it means that the current intensity is too
low.  In this case, you need to press a mouse button to
return to the dialog box and adjust the intensity slide bar
to a higher value.  The color rectangle should be visible
when you re-enter the color selection screen. 

\Shadows

BIG D can calculate shadows cast onto objects by other
objects.  Like Reflections, this feature adds greatly to the
realism and depth perception of the rendered image.  Shadow
calculations also add to the image generation time.

With Shadows on, BIG D calculates shadows cast upon objects
by other objects (as well as shadows cast by an object upon
itself).

Consider toggling Shadows off to save generation time.
Shaded surfaces (surfaces facing away from a light) are
still rendered correctly, but shadows are not cast.

\Show Current Image Operation

The Show Current Image operation button displays the
currently selected image file on the rendering device.

To display an image file, first select the file you wish to
see as the currently selected image.  Then pick the Show
Current Image button.

BIG D transfers control to the rendering device.  It clears
the screen, then quickly reads and displays the image file
for your inspection.

When you have finished viewing the image, press any mouse
button and BIG D will return control to the graphics device
and the Show Image dialog box.

You are now free to show another image or pick the Done
button to exit the Show Image dialog box.

NOTE: BIG D can display 16, 24, and 32 bit images on an 8
bit (256 color) rendering device.  However, some image
quality will be lost in comverting the image to an 8 bit
format.

\Show Image

The Show Image option allows you to display a finished
rendering on the rendering device.  Each rendering is saved
on disk as a TARGA file.  You can display renderings located
on other drives and in other directories.

Selecting Show Image from the File menu causes the Show
Image dialog box to appear.  The Show Image dialog box
contains options for selecting the file type, current drive,
current directory, and image file name.

\Show Image Operation

The Show Image operation button will display the currently 
selected image file on the rendering device.  When the image 
is completely shown, you can press any key or mouse button 
to return to the Show Image dialog box.

Pressing Control-Q while the image is being read from disk 
will abort the reading process.

\Show Lights

The Show Lights option of the Display menu displays all
currently defined lights in the plan and elevation ports.

If all lights are being shown, this option changes to Hide
Lights. Hide Lights will make all currently shown lights
disappear.

\Show Views

The Show Views of the Display menu displays all currently
defined views in the plan and elevation ports.  This allows
you to see each views relationship to the other views.

If all views are being shown, this options changes to Hide
Views. Hide Views will make all currently shown views
disappear.

\Specular Exponent

The specular exponent controls how smooth a shiny surfaces
appears. Very smooth specular surfaces will exhibit very
small, focused specular highlights.  Shiny surfaces which
are rough will show specular highlights which are more
spread out.

The higher the specular exponent, the smoother a shiny
surface will appear and the smaller will be its specular
highlights.

A low specular exponent will result in a rough, shiny
surface.  The specular exponent has no effect if the
specular reflection coefficient is zero.

\Specular Reflection

The specular reflection coefficient determines how shiny a
material is.  Highly specular materials will exhibit shiny
highlights reflected from light sources.

If reflection mapping is turned on, the specular coefficient
also determines how mirrored the material is.  A high
specular coefficient will clearly reflect other objects in
the scene.

Typical specular reflection coefficients are 20 percent for
a waxy floor, 50 percent for a shiny metal, and 80 percent
for a clean mirror.

\Sun

The sun is a special directional light which you can locate
by entering your latitude, day of year, and time of day. BIG
D uses this information to calculate the exact bearing and
altitude of the sun.

You can also specify the direction toward true north, as
well as the sun's hue, saturation, and intensity.  Select
the Sun option of the Lights menu to define the sun.

\Sun Hue

The sun's hue is the color of the sun.  It is defined as an
angle between 0 and 360 degrees.  The angle corresponds to a
color on a color wheel, with red at 0 degrees, green at 120
degrees, and blue at 240 degrees.

You can select the sun's hue by picking an angle on the hue
slide bar or by using the color selection screen (see Select
Color).

A colored sun can be used to simulate sunlight which is
filtered through the atmosphere.  For example, an orange hue
can be used to emulate a setting sun.

\Sun Intensity

The sun's intensity is a measure of the brightness of the
sun.  It is an absolute number (not a percentage) from 0 to
100.  The higher the number, the brighter the sun.

If the sun intensity is set to zero, the sun is disabled and
BIG D assumes that it does not exist.  You must set a
non-zero intensity in order to define the sun.  Typical sun
intensity values range from 30 to 50.  

You can select the sun's intensity by using the slide bars
in the dialog box.

\Sun Saturation

Saturation is the purity or vividness of the color, measured
as a value between 0 and 100 percent.  A pure color is 100%
saturated.  As white is added, saturation decreases.  Zero
saturation gives no color at all, a shade of gray.  

You can select the sun's saturation by picking an angle on
the saturation slide bar or by using the color selection
screen (see Select Color).

\Target Icon Size

The Target Icon Size option sets the size of the target icon
which is drawn in the view ports to represent the location
of a target.  The target icon is drawn as a square with an X
inside.

The size of the target icon is measured in pixels.

\Target and Camera Location

The target and camera locations are specified by their x, y,
and z coordinates.  The unit of measurement is set with the
Units options of the Display menu.

You may adjust the coordinates of either the camera or
target by typing in new ones or by selecting the either
Locate button or the Wire-Frame button at the bottom of the
dialog box.

\Texture File Type

The first line under the title of the Texture dialog box
asks for a file type.  The file type refers to the format of
the texture file, as well as the file's extension.

Select the file type (TGA, WIN, or PIX) of the image to be
assigned to the current material.  The list of available
files in the file scroll box will change depending on the
file type chosen.

\Texture Maps

BIG D allows you to easily map real world textures such as
woodgrain or brick to objects in your AutoCAD drawing.
Texture maps can add a great deal to the realism of a scene.

A texture map is a two dimensional image of a pattern or
object.  Any TARGA format file can be used with BIG D as a
texture map.  A texture map file may be captured with a
video camera, scanned with a scanner, created with a paint
program, or may even be an image generated by BIG D.

You can assign a texture map to any material in the
materials library, although not all materials need or have
texture maps assigned to them.

The Edit Current Material Texture button of the Materials
dialogue box lets you assign or modify a material's texture
map.  The texture dialog box lets you select a texture file
from anywhere on your system (including the BIG D texture
directory).

You can tell BIG D to repeat a texture pattern infinitely so
that it will cover any size object.  You can also set the
rotation angle, width, and height of the texture map.

To assign a texture map to a material in the material
library, first select the material as the current material
in the Materials dialog box.  Then select the Edit Current
Material Texture button to display the Texture dialog box.

The Texture dialog box lets you select the file type, the
name, the repeat mode, the rotation angle, the width, and
the height of the texture map.

\Texture Scroll Box

All appropriate files which reside in the current directory
appear in the Texture scroll box.  If there are more files
available than will fit in the box at one time, you can use
the scroll bar to scroll through the file list.

To select a new current file, move the cursor over the name
of the file you wish to select and press the left mouse
button.  The name will highlight and the Current File line
above will change to show the new file name.

\Transmission Coefficient

The transmission coefficient sets the percentage of light
transmitted through the material.  The coefficient is
measured as a percent of light transmitted per unit
thickness.

The higher the transmission coefficient, the more light is
transmitted through an object.  Completely opaque materials
have a transmission coefficient of zero.

Thin objects transmit more light than thick objects.  A
material with a transmission coefficient of 60 percent will
transmit 60 percent of all light through a 1 unit thick
object.  A 2 unit thick object will only transmit 30 percent
of the light.

Clear glass has a transmission coefficient of about 80
percent.

NOTE: If a light transmitting object has zero thickness
(such as a 3D face), BIG D will reduce the amount of light
passing through it as if it were one unit thick.

\Transmissions

You can assign transparent materials to objects in your
model.  BIG D will calculate the refraction effects of the
light rays as they are transmitted through the material.
This process is called transparency mapping.

Transparency mapping can add significantly to the image
generation time.  The Transmissions option allows you to
reduce generation time by turning off all transparency
calculations.

Turning Transmissions off will cause all objects which are
assigned light transmissive materials to appear opaque.
Turning Transmissions on allows BIG D to calculate
transparency effects.

\Units

The Units option determines the format BIG D uses to display
linear and angular measurements.  Several formats are
available, and most are similar to the formats available
with AutoCAD's UNITS command. 

\Using AutoCAD

Most AutoCAD 3D drawings can be imported into BIG D without
modification.  All you need to do in AutoCAD is create a
drawing interchange (DXF) file.

In addition, BIG D offers enhancements to AutoCAD's 3D
modelling capabilities which save time and produce superior
renderings.

*** Supported Entities ***

AutoCAD entities currently supported by BIG D include LINES,
ARCS, CIRCLES, SOLIDS, 3DFACESand 3DMESHES.  Entity
elevation, thickness, layer, and user coordinate system are
maintained.

BIG D fully supports BLOCKS and BLOCK INSERTIONS.

NOTE: POLYLINES are not currently supported by BIG D.  If
you wish to include polylines in drawings, you must EXPLODE
each polyline into LINES and ARCS.

*** Layers ***

BIG D assigns material properties to entities based on
layers.  In other words, all entities which are drawn on the
same layer will be assigned the same material properties.

Conversely, if you wish to assign different material
properties to different entities, then the entities must be
drawn on different layers.  It is important that you keep
these rules in mind when building your model.

*** Modelling Enhancements ***

BIG D offers enhancements to AutoCAD's 3D modelling which
save time and improve the quality of your renderings.

*** Complex Shapes and Extrusions ***

With BIG D you may easily create complex shapes and
extrusions with holes using only LINES, ARCS, and CIRCLES.
Any collection of LINES and ARCS which form a closed shape
are interpreted by BIG D as a single, solid shape.  Closed
shapes which are inside other closed shapes will form holes.

The endpoints of the individual entities must match exactly,
the entities must reside on the same layer, and the entities
must have the same elevation and thickness.  Closed shapes
completely enclosed by other closed shapes form holes.

BIG D handles extrusions much more efficiently than it does
other types of entities.  You are encouraged to use the
solid extrusion enhancement whenever possible.

*** Surfaces of Revolution ***

If you are using Release 10, you can use AutoCAD's REVSURF
command to generate surfaces of revolution.  However, BIG D
offers a more efficient alternative with two special lisp
routines: BDRSURF.LSP (a drawing tool), and EDRSURF.LSP (an
editing tool).

Before you can generate a surface of revolution, you must
first draw a cross section of the surface using LINES, ARCS,
and/or CIRCLES.  

The cross section must be drawn relative to an axis of
revolution. The axis of revolution is a line parallel to the
local Y axis about which the cross section is to be
revolved.  

NOTE: The entities which make up the cross section MUST be
drawn to the right of the axis of revolution.

If you wish to create a solid object, the cross section must
be drawn as a closed shape.  If the cross section is not a
closed shape, the resulting object will not be solid.
Instead, it will be an infinitely thin shell.

To use BDRSURF and EDRSURF in AutoCAD, you must first load
them using the Autolisp "load" command.  The two lisp
routines reside in the BIG D directory so you must give the
full path name when loading them.

For instance, if the BIG D directory is named "BIGD", you
should enter the following command at the AutoCAD command
prompt to load BDRSURF.

    (LOAD "/BIGD/BDRSURF")

Then type the name of the lisp routine at the next command
prompt to execute the command.

    BDRSURF

BDRSURF creates a block from a series of LINES, ARCS or
CIRCLES which are revolved to represent a surface of
revolution.  The block must be INSERTed for this feature to
work.

BDRSURF asks for a block name, insertion point, angle of
revolution, and the entities to be revolved.  The entities
are revolved about a line parallel to the y-axis through the
insertion point.  The angle of revolution starts at the x-y
plane and moves around the revolution line according to the
right-hand rule.

EDRSURF allows you to easily edit a block created by
BDRSURF.  It re-inserts the original entities which created
the revolved surface. You can add to, subtract from, or
modify the entities.  The block must then be rebuilt with
BDRSURF.

NOTE: Do not insert a block created by BDRSURF as individual
parts (do not precede the block name with a "*") and do not
EXPLODE a block created by BDRSURF.

*** Creating the DXF File ***

BIG D cannot read AutoCAD drawing (DWG) files directly, but
it can read AutoCAD drawing interchange (DXF) files.  For a
drawing to be rendered with BIG D, it must first be saved as
a DXF file.  A DXF file can be created within AutoCAD's
drawing editor by using the DXFOUT command.  See your
AutoCAD Reference Manual for details.

NOTE: If you are using AutoCAD Release 10, you should use
the binary option to create a binary DXF file.  BIG D can
read both ASCII and binary DXF files, but the binary format
has several advantages.  It can be created by AutoCAD and
read by BIG D more quickly than an ASCII DXF file.  Also, a
binary DXF file is smaller than an ASCII DXF file.

\View Operations

The View dialog box offers two operation buttons: Locate and
Wire-Frame.

*** Locate ***

The Locate operation button lets you graphically locate the
current view's target and camera in the plan and elevation
ports.

*** Wire-Frame Operation ***

The Wire-Frame operation button causes BIG D to draw a
wire-frame projection of the model from the current view.
The projection type (parallel or perspective) and lens focal
length depend on the values set in the Rendering Options
dialog box.

The wire-frame projection gives you a preview of what the
model will look like from the current view.  A button panel
to the right of the projection lets you fine-tune the
locations of the target and camera to get exactly the view
you want.

\Views

A view consists of a camera and a target.  The camera is the
point from which you want to view the scene.  The target is
the point toward which you wish to look.

Each view is numbered, beginning with view number 1.  BIG D
generates the image files in the order they are numbered.  

The name of each output image file consists of the base file
name plus a two digit view number, plus the appropriate file
extension (TGA or PIX).  The base file name can be up to
four characters long and defaults to the first four
characters of the input DXF file.

The Views menu offers four options: add a view, insert a
view, delete a view and edit a view.  If no views are
currently defined, only the add a view option is available.

\Views Menu

The Views menu allows you to establish and edit a sequential
list of viewpoints in your 3-D model.  You may add a new
view, insert a new view before an existing view, delete a
view, edit an existing view, and generate any number of
additional frames between any two defined views.

You must define at least one view before generating an
image.  If you define more than one view, BIG D generates an
image file for each view.

\X-ray Light

An x-ray light is a special type of BIG D light that does
not cast shadows. X-ray lights penetrate through objects and
illuminate all surfaces which face the x-ray light.

X-ray light is primarily used to simulate background light
which is reflected off other objects, helping to
differentiate surfaces in shade.  

For example, suppose you have two walls joined at right
angles in an L shape. If only one light (not an x-ray light)
is present, one side of each wall is illuminated and the
other side is in shade.

The shaded sides are illuminated only by ambient light.  If
both walls have the same material properties, the ambient
light illuminates each wall equally, making the intersection
of the walls disappear (because both surfaces have the same
intensity).  

Now suppose you add an x-ray light at a direction roughly
opposite the primary light.  Give the x-ray light a small
intensity, say 10 percent of the primary light.  The x-ray
light now helps the ambient light illuminate the shaded
walls.

But since the x-ray light strikes the two walls at different
angles, it illuminates one wall more than the other, helping
to differentiate the two walls in shade.
