SPHMOD(3L)SPHMOD(3L)NAMEsphmod - set sphere attributes
FORTRAN 77 SPECIFICATION
#include <gl/fsphere.h>
integer*4 function sphmod(attribute, value)
integer*4 attribute
integer*4 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.
DESCRIPTIONsphmod is used to specify the attributes of a sphere.
The sphere attributes and valid settings are as follows:
SPHTES
selects the type of sphere tesselation. Valid settings for
tesselation are: SPHOCT, SPHICOS, SPHBAR, SPHCUB, and SPHBIL. 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 SPHOCT.
SPHDEP
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 SPHMXD, inclusive. The default sphere
depth is 5.
SPHPRI
selects the GL drawing primitive. Valid settings for sphere
primitive are: SPHPOL, SPHMSH, SPHLIN, and SPHPNT. When the
primitive attribute is set to SPHPOL, independent triangles or quads
are drawn, depending on the sphere tesselation type. When using
SPHMSH, tmeshes or qstrips are used. The default value for the
sphere primitive is SPHMSH.
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SPHMOD(3L)SPHMOD(3L)
SPHHEM
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 SPHORI attribute.
The default value is FALSE, meaning that full spheres are drawn.
SPHORI
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 sphrma 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, sphdra, sphfre, sphgnp, sphobj, sphrma
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