PC Shareware 2000 January/PCShareware-1-00.iso/s3d/SIMPLY3D/DOCS/UG_LIGHT.DP

Common Ground | 1995-02-17 | 77.0 KB | 354 lines

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The Light Designer
MIn addition to ambient light (assigned in the View Designer),  Renderize Live
*2NEZ provides for several types of directional light sources. The Light Designer
*2Mwindow is used to create and edit lights for the current project.  Lights are
*2Hdisplayed as part of a view in wireframe mode so that their position and
*2Qorientation can be changed easily in relation to the other resources in the view.
*AQLight sources themselves are not rendered.  The effects of these light sources on
*2Hobjects (light color, sheen, shading and shadowing) are displayed in the
*2;rendered view, but the lights themselves are not displayed.
*APEach light resource is displayed as an icon in the Light Resource Palette on the
*2KResource Manager area of the Project Designer.  Different icons are used to
*2Srepresent different kinds of lights (point, spot, area, area spot), and attenuation
*2&and shadow properties are also noted.
*AJA light is independent of any view in which it may be included, and can be
*2Lincluded in more than one view of a given project.  When a light is changed,
*2Sthat change is reflected in any views that contain that light resource.  Lights are
*2Gsaved within projects and not in external files and are, therefore, not
*2+transferable from one project to another.
Light Designer Overview
*cMThere are several basic light types that can be defined in Renderize Live EZ.
These include the default
point
light
)R', which shines light in every direction
from its point location; a
spotlight,
, which casts a beam of light from its source
t%in a direction aimed at a target; an
area light
#, which is a group of light sources
tGorganized together, much like the outdoor lights at a ballpark; and an
t    spotlight
F, which combines the characteristics of a spotlight and an area light.
tKGenerally speaking, area lights cast flatter light and more diffuse shadows
*2:because the light intensity is spread over a larger area.
*ARIn addition to assigning the type of light source, the Light Designer is also used
*2Pto assign a number of properties individually to each light source.  A light can
be set to
cast shadows
; a light can be set to
Y    attenuate
, so that the intensity of
tJlight diminishes as it gets farther from the light source; and finally, a
color
t    intensity
 can be defined for the light.
t7Lights can be positioned and oriented by typing in the
 and
Position
Target/Rotation
? coordinates using the type-ins provided in the Light Designer.
tJHowever, because the orientation of a light in a view often depends on the
*2Rposition of the objects and the camera in that view, lights are usually positioned
*2Oin the viewport of the Project Designer after having been added to a particular
*2Nview.  When a light resource is added to a view, a wireframe representation of
The Light Designer
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Qthat light appears in the view to represent that light's position and orientation
*2Lin 3D space.  This wireframe light can be manipulated in the viewport of the
*24Project Designer in the same way as other resources.
*ANThe Light Designer is opened, closed and controlled in the same way as each of
*2Fthe other Resource Designer Windows.  For a complete discussion of the
*2Pgeneral loading, saving, renaming, etc, of resources, as well as a discussion of
*2Uthe different kinds of control entities (wells, buttons, type-ins, etc), please refer
*24to the Renderize Live EZ Interface Overview chapter.
The Default Light Source
*cQIf the Light Designer is opened by dropping the "default" light resource into the
*2PEdit Well of the Project Designer, then the properties in the Light Designer are
*2Rupdated to the default settings.  The default light source is a point light, which
*2Sis similar to a bare light bulb in that it shines in all directions from a point in
*2Mspace.  The light source casts no shadows, and does not attenuate.  The light
*2Ncolor/intensity is pure white.   The position of the light source is above the
*2Mdefault camera position, and located far behind the plane of the camera.  The
*2Rlocation of the light source far back from the area of interest serves to simulate
illumination from the sun.
Light Types
*cMThe Light Types area at the top of the Light Designer is where you choose the
*2(basic light type that you wish to use.
The Point Light Option
*PUA point light is the simplest light type.  It can be likened to a bare lightbulb that
*2Dshines light equally in all directions from a single point in space.
*AOA point light source appears in the Project Designer as a spherical icon with a
*2Ptail attached.  The tail does not represent direction, since a point light casts
*2Slight in all directions: instead, it is simply used to find the light in situations
*2Gwhere the light icon is located beyond the extants of the current view.
The Spotlight Option
*PLSelect this option to create a light that shines in a specific direction.  A
*2Sspotlight creates a cone of light that can be aimed at a given target.  The size of
*2Rthe light cone and the intensity of light in the cone can be manipulated to create
*2Na variety of spotlight effects.  Spotlights speed up the rendering of an image
*2Qthat has shadows, since the area of a view illuminated by a spotlight is limited.
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tNA spotlight appears in the Project Designer viewport as a spotlight icon, with
*2Itwo sets of red lines emanating from the light.  These lines indicate the
*2Ndirection of the spot.  The inside set of lines represent the Hot Angle of the
*2Tlight, and the outside set of lines represent the Soft Angle of the light.  Unlike a
*2Lpoint light, which casts light in every direction, a spot light is targeted;
*2Rtherefore the light must be oriented such that it illuminates the desired subject.
*APWhen you select the Spotlight option, two dials appear to define the light beam:
)M    Hot Angle
     and the
Soft Angle
..  In addition to modifying these values here,
t@you can also set them visually in the Project Designer viewport.
The Soft Angle Dial
*PRThis dial defines the spread, in degrees, of the entire beam of light projected by
*2Mthe spotlight.  Click and hold down on this dial and move the mouse to change
*2Lthe angle, and release when the desired angle is displayed.  A setting of 60
*2Kdegrees means the beam of light emits from the source at a 60 degree angle.
*2SAny objects falling within the arc created by this angle are lighted by this light;
*2,objects outside of the arc receive no light.
*ANThe area of light emitted by a spotlight depends on 2 factors: the size of the
*2OSoft Angle and the distance from the light source to the target.  The wider the
*2PSoft Angle, the larger the arc of light, and that arc increases as distance from
the light source increases.
The Hot Angle Dial
*PPThis dial defines the angle of the full intensity beam of light projected by the
*2Mspotlight.  Click and hold down on this dial and move the mouse to change the
*27angle, and release when the desired angle is displayed.
*AIThe Hot Angle refers to the area within the Soft Angle in which the light
*2Pshines at its full intensity.  The area between the Hot Angle and the Soft Angle
*2Tis the "fall-off" area, or the area at which the light graduates from full intensity
*2Oto zero intensity (or no visible light) as it moves out to the edge of the Soft
Angle.
*ASIt is not possible to define a Hot Angle that is wider than the Soft Angle.  If you
*2Oraise the Hot Angle above the Soft Angle value, the Soft Angle dial will update
*2Lso that it equals the highest Hot Angle value.  If you reduce the Soft Angle
*2Obelow the Hot Angle value, the Hot Angle dial will update so that it equals the
lowest Soft Angle value.
*APUsing the Soft Angle and Hot Angle dials together, different kinds of spotlights
*2Kcan be created.  If Soft and Hot Angles are about the same, the result is a
*2Kspotlight with highly defined edges.  If Soft Angle is far greater then Hot
*2IAngle, the result is a spotlight that gradually fades to black around the
perimeter of the cone.
The Light Designer
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The Area Light Option
*POSelect this option to create an area light.  An area light actually consists of
*2Nmultiple point light sources grouped together to create the effect of one very
*2?large light source.  Area lights are used to cast soft shadows.
*AMAn area light appears as a box in the Project Designer.  If the area light is
*2Edefined using spotlights, the light direction is represented as well.
*B When this option is selected, a
Sample
# dial appears, as well as a set of
Scale
 type-ins.
The Samples Dial
*PRUse this dial to indicate the number of light sources in the area light.  The more
*2Qlights sources that exist, the better the shadows will appear, but at the expense
of rendering time.
*AMNote that increasing the number of samples does not increase the intensity of
*2Pthe light: the intensity, determined in the Light Color/Intensity well, is split
*2+evenly among all samples in the area light.
The Area Scale Type-Ins
*PKThe dimensions of an area light are defined using the X, Y and Z Area Scale
*2Mtype-in boxes.  The larger the scale, the more lights it can contain, and the
*2 larger the area of illumination.
*APGenerally speaking, the samples in an area light are all positioned on one plane
*2K(defined using the X and Y Area Scale type-ins).  However, in some cases it
*2Omay be desirable to assign depth to an area light: in this case, use the Z Area
Scale type-in also.
The Area Spotlight Option
*PLSelect this option to create an area light with directional properties and a
*2Pfall-off area.  This option combines the effects of the Spotlight and Area light
options discussed above.
Light Options
*cKThe Light Options area of the Light Designer allows you to define shadowing
*2Pand attenuation properties for the current light, and to enable the simultaneous
*2$display of all the lights in a view.
The Light Designer
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The Casts Shadow Option
*POSelect this option if you want the current light to cast a shadow.  When shadow
*2Icasting is enabled for a light, the word "SHAD" will appear on that light
source's postage stamp icon.
*AQEven if this option is selected, the light will not cast a shadow until two other
*2Mconditions are met: the object(s) in the light's path must be defined to cast
*2Ishadows (a selection in the Object Designer), and shadows must be enabled
*2Kglobally for rendering (a selection under the Render Toolbox of the Project
Designer).
*ARShadows are only cast onto objects, and only if the object is defined to receive a
*2Lshadow (a property defined in the Object Designer).  A shadow cannot be cast
*2Monto a background image.  Therefore, for a light to cast a shadow, there must
*2Mbe two objects: one object onto which the shadow is cast, and another object,
*2Nlocated between the light and the first object, which casts the shadow.  There
*2Pare cases where an object can cast a shadow onto itself, due to the shape of the
*2=object and/or the self-shadow bias setting (described below).
*ALWhen the Casts Shadow button is enabled, several additional commands related
*2Fto shadow casting appear in the Light Designer window.  These commands
include
    Intensity
Self Shadow Bias
 and
Shadow Map Size
The Intensity Dial
*PRUse this dial to control the intensity of the shadow that is cast.  The higher the
*2Rvalue, the darker the shadow is that is cast; the lower the value, the lighter the
shadow.
*AMShadow intensity can also be affected by changing the amount of ambient light
*2Hin the scene (ambient light is manipulated in the View Designer window).
*2NRaising the ambient light will effectively reduce the intensity of the shadow.
*2OHowever, it will also make the scene appear more flatly lit, and therefore less
*2    dramatic.
The Self Shadow Bias Type-in
*PKThis type-in is used to determine at which point an object begins casting a
*2Oshadow.  Values here range from 0.0 to 1.0: at 0.0 an object will cast a shadow
*2Ponto itself; at 1.0 an object will cast no shadows.  The default value of 0.1 is
*2Ocorrect for most cases, but there are situations where the value may need to be
*2    modified.
*ALIf after rendering a view, the shadow cast by an object seems to fall in the
*2Pwrong place or be incorrectly shaped, try decreasing the self shadow bias value.
*2OIf the object casting the shadow seems to cast a shadow onto itself, or appears
*2Lwith irregularly shaded polygons, try increasing the self shadow bias value.
The Light Designer
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The Shadow Map Size Type-in
*PKThis determines the size of the shadow map that is generated for this light
*2Jwhen a view is rendered.  The larger the shadow map size defined here, the
*2Dsharper the shadow will be, but at the expense of rendering speed.
*AFThe optimum size for the shadow map depends on the area over which the
*2Kshadow map must be calculated in relation to the area visible in the camera
*2Rview.  If objects exist outside the camera view, and these objects are set to cast
*2Mshadows, then a shadow map must be calculated over this entire area, and only
*2Ja subset of this map is displayed in the camera view.  The result may be a
*2Oshadow with jagged edges.  Therefore, be sure to disable shadow casting for any
*2Nobjects that are outside the camera view so that the shadow map is cast over a
*29smaller area, resulting in a finer edge during rendering.
*AGThe default shadow map size value is 128. If after rendering a view the
*2Dshadows appear "jaggy" or pixelated, try increasing the shadow size.
The Attenuated Option
*PQSelect this option if you want the current light to be attenuated.  An attenuated
*2Slight is one which loses intensity as the distance from the light source increases.
*2NAttenuation also increases the sense of depth in a view, but at the expense of
*2Prendering time.  An attenuated light is useful to cast light on some objects but
*2Nnot on others.  When attenuation is enabled for a light, the word "ATTEN" will
*21appear on that light source's postage stamp icon.
*BMWhen attenuation is enabled, two dials appear to define the attenuation: the
Distance
 dial and the
Fade Distance
& dial.  In addition to modifying these
Kvalues here, you can also set them visually using your mouse in the Project
Designer viewport.
The On Distance Dial
*PNDefine the distance from the light source at which attenuation begins.  If the
*2Nlight should begin losing intensity immediately after emanating from the light
*2=source, use a low number here; otherwise use a larger number.
The Fade Distance Dial
*PMDefine the distance from the On Distance dial at which the intensity fades to
*2Jzero, or no light.  The light in the area between the On Distance and Fade
*2NDistance values will fade in intensity, until it reaches zero intensity at the
*2Gdistance defined by the sum of the Fade Distance and On Distance dials.
*AMWhen an attenuated light appears in the viewport of the Project Designer, two
*2Oplanes appear associated with that light's "target beam": one at the defined On
*2IDistance and the other at the defined On Distance plus the Fade Distance.
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tMThese planes help you to determine visually whether or not your target object
*2"will be illuminated by this light.
The Show All Lights Option
*PMNormally, when working with a view in the viewport of the Project Designer, a
*2Olight will not appear unless it is dropped into the Edit Well for manipulation.
*2FWhen the Show All Lights option is selected on the Light Designer, the
*2Owireframe icons for each of the lights is displayed in the viewport, along with
*2Qlines that represent their "target".  This allows you to see the position of each
*2Llight in relation to the other, but on the other hand it may add unnecessary
*2Oclutter to the wireframe view.  Of course, the only light whose orientation can
*2Abe modified is still the light that is loaded into the Edit Well.
'Defining a Light's Color and Intensity
*cNThe color and intensity of a light are defined using the Light Color/Intensity
*2QWell at the lower left corner of the Light Designer.  To define a color, move the
*2Mpointer over this Well and select the left mouse button: the Color Toolbox is
*2Mdisplayed, and any changes you make in that Toolbox are reflected immediately
*2"in the Light Color/Intensity Well.
*AQThe light intensity is controlled using the "value" slider in the Color Toolbox's
*2N"hsv" color selection mode.  A value of 1 gives you a light at 100% intensity;
*24any values below 1 reduce the strength of the light.
Positioning a Light
*dBThe position of a light in a view can be changed by typing in new
 and
Position
H coordinates.  Similarly, the direction in which a light points can also
be typed in using the
 and
Z Target
% coordinates.  Target coordinates are
tRonly relevant if the current light source is a spotlight, or an area light made up
*2Sof spotlights.  The direction that a light points can also be expressed in terms of
rotation.  Select on the
Target
)z/ title above the coordinate type-ins and select
Rotation
I; the values in the type-in will update to display the direction in which
tGthe light faces.  Now when you enter values in these type-ins, they are
*2&expressing the rotation of that light.
*ALWhile these type-ins allow for extremely precise positioning of lights in 3D
*2Uspace, it is often easier to position the lights visually with in the viewport of the
*2OProject Designer.  To position a light source in the Project Designer, drag the
*2Kdesired light from the Lights Resource Area and drop it into the Edit Well.
*2GThe mouse can now be used to position the light within the View.   This
*2Rmethod of positioning lights visually is described in full in the Project Designer
Window chapter.
The Light Designer
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RRemember that the position of a light is a property of that light: if you change a
*2Qlight's position in one view, that orientation is changed in all other views that
*2Pcontain that light.  If you have a case where a single light must have different
*2Opositions in different views of the same project, make a copy of that light (by
*2Ldropping it into the Light Designer and renaming it) before incorporating it
into subsequent views.
Lighting and Views
*cQThe type, position and color of a light all have an important effect on the final
*2Rresults of a rendered view.  In addition, the distance that a light is placed from
*2Uthe objects in the view greatly affects the way the view is lit, even if the light is
*2Unot attenuated.  If a light source is placed far from the area of interest in a view,
*2Mthe light generated by this light source is more diffuse, effecting all areas
*2Qequally.  If the light source is very close to an object, that object will appear
*28with hot spots where the object is closest to the light.
*AOWhile the choice of objects, the materials and textures applied to them and the
*2Ocamera angle and viewpoint determine the contents of a view, it is the lighting
*2Sthat brings it to life.  Intricacy of lighting can be the most important element in
*2Jfocusing attention within a view and creating interest.  A difficulty with
*2Qcomplex lighting is that the results of various combinations of lights is hard to
*2Jpredict with accuracy.  Practice and experience can reduce the effort, but
*2Hexperimentation is still the only reliable method of determining optimum
*2Llighting.  If there is to be a series of views of a similar type, a standard
*2Mcombination of lights may be developed and reoriented as a group, rather than
each light individually.
The Light Designer
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Windows 3.10 (Maker 1.03)
Nick Josephs

Visual Software, Inc.

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