bgnpolygon(3G)bgnpolygon(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.
Page 1
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.
Page 2
