endpolygon(3G)

NAME
     bgnpolygon, endpolygon - delimit the vertices of a polygon

C SPECIFICATION
     void bgnpolygon()

     void endpolygon()

PARAMETERS
     none

DESCRIPTION
     Vertices specified after bgnpolygon and before endpolygon form a single
     polygon.  The polygon can have a maximum of 256 vertices.  Use the v
     subroutine to specify a vertex. Self-intersecting polygons (other than
     four-point bowties) may render incorrectly.  If a quadrilateral projects
     a self-intersecting polygon, its rendering will be hardware-specific. The
     Graphics Library only guarantees that pixels outside of the convex hull
     will not be modified.  Also, concave polygons may not render correctly if
     you have not called concave(TRUE).

     Between bgnpolygon and endpolygon, you can issue only the following
     Graphics Library subroutines:  c, color, cpack, lmbind, lmcolor, lmdef,
     n, RGBcolor, t, and v.  Use lmdef and lmbind to respecify only materials
     and their properties.

     By default polygon vertices are forced to the nearest pixel center prior
     to scan conversion.  Polygon accuracy is improved when this coercion is
     defeated with the subpixel command.  Subpixel vertex positioning is
     especially important when polygons are scan converted with antialiasing
     enabled (see polysmooth).

     After endpolygon, the current graphics position is undefined.

SEE ALSO
     backface, c, concave, frontface, polymode, polysmooth, scrsubdivide,
     defpattern, shademodel, subpixel, v

NOTES
     If you want to use the backface or frontface routines, specify the
     vertices in counter-clockwise order.

     Although calling concave(TRUE) will guarantee that all polygons will be
     drawn correctly, on the IRIS-4D B and G models, the Personal Iris, Iris
     Entry, Indy, XL, XS, XS24, XZ, Elan, and Extreme systems, doing so causes
     performance to be degraded.

     See the section, "2.1.4 Polygons," in the Graphics Library Programming
     Guide for a discussion on the handling of non-coplanar and/or self-
     intersecting polygons.
     On Impact and Infinite Reality lmcolor cannot be called between
     bgnpolygon and endpolygon

     On Impact and Infinite Reality concave(TRUE) severly hurts performance
     and some non-simple four sided polygons cannot be handled correctly.