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-
- SURFC, Introduction
-
- There are three types of surfaces which the user can define in
- QD3D. They are : planes, cylinders and revolved arcs.
-
- Planes are flat areas with straight lines or circles (i.e. arcs
- or one full circle) as edges.
-
- Cylinders are "right circular cylinders" or "right circular
- cones" and thus the term "cylinders" is used in QD3D to mean
- both cylinders and cones (unless explicitly differentiated).
-
- Both can be represented by the path swept by a straight line as
- it rotates about a rotation axis.
-
- A revolved arc is the path swept by an arc as it rotates about a
- rotation axis. For example a semi-circle rotated by 360o about
- a line which passes through the ends of the arc, will generate a
- sphere. A circle rotated by 360o about some line external to
- the sphere will generate a torus.
-
- When the SURFC command is selected the user can manipulate the
- current surface type : for example adding, deleting, changing
- etc. The current surface type is displayed in a tertiary menu
- which can be altered by the SURFC TYPE command. The tertiary
- menu will look like:-
-
-
- Plane
-
- Cylinder
-
- Rev. Arc
-
-
-
- Note: When the tertiary menu is altered the secondary menu is
- automatically altered to suit the new default surface type.
-
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-
- SURFC (PLANE), Introduction
-
- Planes are areas defined by the user which may be free-standing
- or incorporate existing features of the drawing.
-
- Planes are a very essential building block in QD3D. Whenever the
- user does a hidden edge or hidden (shaded) surface calculation,
- QD3D uses the relative position of the planes to draw the desired
- result.
-
- Once created, planes can be moved as complete elements, and can
- be modified by suitable manipulation of any of the individual
- defining points.
-
- When the command DRAW PLANE is executed, a small diamond is drawn
- at the average corner point of each individual plane. There are
- two ways to locate planes:
-
- 1. Locate one of the plane defining points with the alternate
- button.
- 2. Locate the plane centroid diamond with the selection
- button.
-
- In option 1, the user may inadvertently locate a point that
- belongs to more than one plane.
-
- Planes cannot be hatched or filled in QikDraw 3D because the
- screen would become too cluttered.
-
-
- "PLANE ADD"
-
- Planes can be added by locating points on the screen (which may
- or may not currently exist). By default, the plane will always
- close itself from the last point added to the first point added.
- Note that the points used to define a plane are drawn as small
- squares rather than small crosses for the sake of clarity.
-
- Procedure
- . Locate the points to define the plane pressing the
- termination button to finish.
-
-
- "PLANE DEL"
-
- Planes can be deleted just like any other entity. The user
- locates the plane by snapping to a defining point or locating its
- centroid diamond with the selection button and that plane is
- deleted.
-
-
- "PLANE CHANG"
-
- When this command is selected a tertiary menu will appear which
- allows the current values of colour and layer to be changed.
- This tertiary menu also allows the colour and/or layer of a group
- of planes to be changed. The method of locating the group is at
- the top of the tertiary menu (see POINT CHANG).
-
-
- "PLANE OUTLN"
-
- This command allows the user to create planes using current
- entities to define the plane. Unlike PLANE TRACE below, a plane
- can be created with holes in the middle and with circles/arcs as
- definition entities. This OUTLN command is used for planes that
- are to be defined using lines and circles.
-
- Any group of entities being traced must form a closed loop.
-
- If, when the first loop has been traced, a hole o be defined
- within the plane, answer yes to the "more points?" prompt and
- trace around the inner shape as before.
-
- Procedure
- . Locate a line or circle/arc. QikDraw adds plane points at the
- start and end of this entity. Continue this selection of
- entities until the loop