endsurface(3G)endsurface(3G)NAME
bgnsurface, endsurface - delimit a NURBS surface definition
C SPECIFICATION
void bgnsurface()
void endsurface()PARAMETERS
none
DESCRIPTION
Use bgnsurface to mark the beginning of a NURBS (Non-Uniform Rational B-
Spline) surface definition. After you call bgnsurface, call the routines
that define the surface and that provide the trimming information. To
mark the end of a NURBS surface definition, call endsurface.
Within a NURBS surface definition (between bgnsurface and endsurface) you
may use only the following Graphics Library subroutines: nurbssurface,
bgntrim, endtrim, nurbscurve, and pwlcurve. The NURBS surface definition
must consist of exactly one call to nurbssurface to define the shape of
the surface. In addition, this call may be preceeded by calls to
nurbssurface that specify how texture and color parameters vary across
the surface. The call(s) to nurbssurface may be followed by a list of
one or more trimming loop definitions (to define the boundaries of the
surface). Each trimming loop definition consists of one call to bgntrim,
one or more calls to either pwlcurve or nurbscurve, and one call to
endtrim.
The system renders a NURBS surface as a polygonal mesh, and calculates
normal vectors at the corners of the polygons within the mesh. Therefore,
your program should specify a lighting model if it uses NURBS surfaces.
If your program uses no lighting model, all the interesting surface
information is lost. When using a lighting model, use lmdef and lmbind
to define or modify materials and their properties.
EXAMPLE
The following code fragment draws a NURBS surface trimmed by two closed
loops. The first closed loop is a single piecewise linear curve (see
pwlcurve), and the second closed loop consists of two NURBS curves (see
nurbscurve) joined end to end:
bgnsurface();
nurbssurface(. . .);
bgntrim();
pwlcurve(. . .);
endtrim();
bgntrim();
nurbscurve(. . .);
nurbscurve(. . .);
endtrim();
endsurface();
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endsurface(3G)endsurface(3G)NOTE
On Impact and Infinite Reality lmcolor cannot be called between
bgnsurface and endsurfaceSEE ALSO
nurbssurface, bgntrim, nurbscurve, pwlcurve, setnurbsproperty,
getnurbsproperty
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