SPHMODE(3L)SPHMODE(3L)NAMEsphmode - set sphere attributes
C SPECIFICATION
#include <gl/sphere.h>
int sphmode(attribute, value)
int attribute, value;
PARAMETERS
attribute
the sphere attribute to set
value the value to which the attribute is to be set
FUNCTION RETURN VALUE
Returns -1 if an invalid attribute or value is specified, 0 otherwise.
DESCRIPTIONsphmode is used to specify the attributes of a sphere.
The sphere attributes and valid settings are as follows:
SPH_TESS
selects the type of sphere tesselation. Valid settings for
tesselation are: SPH_OCT, SPH_ICOS, SPH_BARY, SPH_CUBE, and
SPH_BILIN. These constants correspond to algorithms that tesselate a
sphere into polygons based on the following types of tesselation:
octahedral, icosahedral, barycentric, cubic, and bilinear
tesselation. The octahedral, icosahedral, and cubic methods
tesselate by subdividing the original faces of the base form. The
barycentric method guarantees that all of the triangles have equal
area and has the same number of triangles as the octahedral
tesselation. The bilinear tesselation is the traditional
longitude-latitude method. The default tesselation is SPH_OCT.
SPH_DEPTH
sets depth of sphere tesselation. The number of polygons in a sphere
is a function of the tesselation type, depth, and primitive used.
Higher depth values result in more polygons, and hence a smoother
looking sphere that takes longer to draw. Valid settings for sphere
depth are any value from 1 to SPH_MAXDEPTH, inclusive. The default
sphere depth is 5.
SPH_PRIM
selects the GL drawing primitive. Valid settings for sphere
primitive are: SPH_POLY, SPH_MESH, SPH_LINE, and SPH_POINT. When
the primitive attribute is set to SPH_POLY, independent triangles or
quads are drawn, depending on the sphere tesselation type. When
using SPH_MESH, tmeshes or qstrips are used. The default value for
the sphere primitive is SPH_MESH.
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SPHMODE(3L)SPHMODE(3L)
SPH_HEMI
toggles the hemisphere attribute. When TRUE, less than the entire
sphere may be drawn, but all of the non-negative Z portion of the
sphere from its canonical orientation will be drawn. Use of this
attribute can improve performance when using the SPH_ORIENT
attribute. The default value is FALSE, meaning that full spheres
are drawn.
SPH_ORIENT
to toggle the fixed-orientation attribute. When TRUE, spheres will
be displayed in a fixed orientation. This means that when viewing
rotations are done, the center of a sphere is transformed to its
correct position, and the sphere surface is drawn in a fixed
orientation. The default orientation is the canonical orientation
unless specified by user with the sphrotmatrix cmd. Use of this
attribute can reduce some lighting artifacts. When the value of
SPH_ORIENT is TRUE, the Sphere Library assumes uniform scaling.
When doing non-uniform scaling in viewing transformations the
results are undefined. The default value is FALSE so that spheres
can be manipulated freely by all matrix operations.
SEE ALSO
libsphere, sphdraw, sphfree, sphgnpolys, sphobj, sphrotmatrix
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