DFASW(3g) — Subroutines

Name

DFASW − Defines a 2D fill area set with shape flag primitive.

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

Syntax

DFASW (SHAPE, N, IXA, PXA, PYA)

Argument     Data Type      Access   Description
---------------------------------------------------------------------------
SHAPE        Integer        Read     Shape of the facets
N            Integer        Read     Number of point lists
IXA          Array of       Read     List of starting indexes for the points
             integers
PXA, PYA     Array of       Read     Coordinates of the points, in
             reals                   modeling coordinates
---------------------------------------------------------------------------

Constants

Defined Argument   Constant   Description
---------------------------------------------------------------------------
SHAPE              DSHPCX     Some facets are self-intersecting
                   DSHNON     Some facets are concave, but none are
                              self-intersecting
                   DSHCON     All facets are convex
                   DSHUNK     Unknown whether any facets are
                              self-intersecting
---------------------------------------------------------------------------

Description

DFASW creates a structure element that uses a list of points to define a two-dimensional fill area set primitive.

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

The DFASW function specifies the two-dimensional (x and y) form of the fill area set with shape flag primitive. The default z-coordinate of the primitive is 0. The function, along with its attributes, draws a complex polygon. You can define both the interior and exterior (edge) attributes of the polygon.

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

•Digital PHIGS generates a set of polygonal areas made up of a collection of subareas.

•Digital PHIGS closes any unclosed polygon (subarea), implicitly.

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

Attribute values control whether or not edges appear in the display.

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

•For a specified point, a straight line is created starting at that point and continuing on 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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DFASW(3g) — Subroutines

Name

Syntax

Constants

Description

See Also