sphmod(3L)

NAME
     sphmod - 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.

DESCRIPTION
     sphmod 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.
     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