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3.5.4 Options Controlling Polygon Rasterization


The interpretation of polygons for rasterization is controlled using

void PolygonMode ( enum face, enum mode ) ;

face is one of FRONT, BACK, or FRONT_AND_BACK, indicating that the rasterizing method described by mode replaces the rasterizing method for front facing polygons, back facing polygons, or both front and back facing polygons, respectively. mode is one of the symbolic constants POINT, LINE, or FILL. Calling PolygonMode  with POINT causes certain vertices of a polygon to be treated, for rasterization purposes, just as if they were enclosed within a Begin ( POINT) and End  pair. The vertices selected for this treatment are those that have been tagged as having a polygon boundary edge beginning on them (see section 2.6.2). LINE causes edges that are tagged as boundary to be rasterized as line segments. (The line stipple counter is reset at the beginning of the first rasterized edge of the polygon, but not for subsequent edges.) FILL is the default mode of polygon rasterization, corresponding to the description in sections 3.5.1, 3.5.2, and 3.5.3. Note that these modes affect only the final rasterization of polygons: in particular, a polygon's vertices are lit, and the polygon is clipped and possibly culled before these modes are applied.

Polygon antialiasing applies only to the FILL state of PolygonMode . For POINT or LINE, point antialiasing or line segment antialiasing, respectively, apply.

David Blythe
Sat Mar 29 02:23:21 PST 1997