DFAW3(3g) — Subroutines

Name

DFAW3 − Defines a 3D fill area 3 with shape flag primitive.

Operating States: PHOP, ∗, STOP, ∗
Digital PHIGS extension function
Creates a structure element

Syntax

DFAW3 (SHAPE, N, PXA, PYA, PZA)

Argument     Data Type      Access   Description
---------------------------------------------------------------------------
SHAPE        Integer        Read     Shape of the facets
N            Integer        Read     Number of points
PXA, PYA,    Array of       Read     Coordinates of the points, in
PZA          reals                   modeling coordinates
---------------------------------------------------------------------------

Constants

Defined Argument   Constant   Description
---------------------------------------------------------------------------
SHAPE              DSHPCX     Facet is self-intersecting
                   DSHNON     Facet is concave, but not self-intersecting
                   DSHCON     Facet is convex
                   DSHUNK     Facet shape unknown
---------------------------------------------------------------------------

Description

DFAW3 uses a list of points to define a three-dimensional fill area 3 with shape flag primitive.

Depending on the current edit mode, this function either inserts the new structure element directly after the element indicated by the pointer or replaces the element indicated by the pointer. The pointer then points to the new fill area 3 with shape flag element.

The DFAW3 function, with its bound attributes, defines a polygon interior in three-dimensional (x, y, and z) form. The polygon may be filled but does not have edges. (Compare this function to the fill area set functions, which define polygon interiors and edges.)

A call to this function has the following effects during structure traversal:

•Digital PHIGS generates a three-dimensional polygon interior.

•Digital PHIGS closes any unclosed polygon, implicitly.

•Digital PHIGS binds the current values of the fill area interior attributes, as defined in the PHIGS traversal state list, to the fill area 3 with shape flag primitive.

If Digital PHIGS clips an area, it generates new boundaries for the area as part of the displayed interior. Whether Digital PHIGS actually displays these boundaries depends upon the current HLHSR mode. The PSIR interior style setting (for example, HOLLOW) also affects boundary representation.

The interior of a fill area 3 with shape flag primitive is defined as follows:

•For a specified point, a straight line is created starting at that point and continuing to infinity.

•If the number of intersections between the straight line and the fill area boundary is odd, the point is within the fill area.

•If the number of intersections between the straight line and the fill area boundary is even, the point is outside the fill area.

•If the straight line passes through a fill area vertex tangentially, the intersection count is not affected.

The shape flag allows Digital PHIGS to use a more efficient fill algorithm for simple polygons.

If Digital PHIGS is in immediate mode, it performs this function immediately, but the function does not create a structure element.

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DFAW3(3g) — Subroutines

Name

Syntax

Constants

Description

See Also