bgnpolygon(3G)							bgnpolygon(3G)

NAME    [Toc]    [Back]

     bgnpolygon, endpolygon - delimit the vertices of a	polygon

C SPECIFICATION    [Toc]    [Back]

     void bgnpolygon()

     void endpolygon()

PARAMETERS    [Toc]    [Back]

     none

DESCRIPTION    [Toc]    [Back]

     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    [Toc]    [Back]

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

NOTES    [Toc]    [Back]

     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 selfintersecting
 polygons.





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bgnpolygon(3G)							bgnpolygon(3G)



     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.


									PPPPaaaaggggeeee 2222