endpol(3G)endpol(3G)NAME
bgnpol, endpol - delimit the vertices of a polygon
FORTRAN 77 SPECIFICATION
subroutine bgnpol
subroutine endpolPARAMETERS
none
DESCRIPTION
Vertices specified after bgnpol and before endpol 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 concav(.TRUE.).
Between bgnpol and endpol, you can issue only the following Graphics
Library subroutines: c, color, cpack, lmbind, lmcolo, lmdef, n, RGBcol,
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 subpix command. Subpixel vertex positioning is
especially important when polygons are scan converted with antialiasing
enabled (see polysm).
After endpol, the current graphics position is undefined.
SEE ALSO
backfa, c, concav, frontf, polymo, polysm, scrsub, setpat, shadem,
subpix, v
NOTES
If you want to use the backfa or frontf routines, specify the vertices in
counter-clockwise order.
Although calling concav(.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.
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endpol(3G)endpol(3G)
On Impact and Infinite Reality lmcolor cannot be called between bgnpol
and endpol
On Impact and Infinite Reality concav(.TRUE.) severly hurts performance
and some non-simple four sided polygons cannot be handled correctly.
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