GLEVALCOORD(3G) UNIX Programmer's Manual GLEVALCOORD(3G)
NAME
glEvalCoord1d, glEvalCoord1f, glEvalCoord2d, glEvalCoord2f,
glEvalCoord1dv, glEvalCoord1fv, glEvalCoord2dv,
glEvalCoord2fv - evaluate enabled one- and two-dimensional
maps
C SPECIFICATION
void glEvalCoord1d( GLdouble u )
void glEvalCoord1f( GLfloat u )
void glEvalCoord2d( GLdouble u,
GLdouble v )
void glEvalCoord2f( GLfloat u,
GLfloat v )
PARAMETERS
u Specifies a value that is the domain coordinate u to the
basis function defined in a previous glMap1 or glMap2
command.
v Specifies a value that is the domain coordinate v to the
basis function defined in a previous glMap2 command. This
argument is not present in a glEvalCoord1 command.
C SPECIFICATION
void glEvalCoord1dv( const GLdouble *u )
void glEvalCoord1fv( const GLfloat *u )
void glEvalCoord2dv( const GLdouble *u )
void glEvalCoord2fv( const GLfloat *u )
PARAMETERS
u Specifies a pointer to an array containing either one
or two domain coordinates. The first coordinate is u.
The second coordinate is v, which is present only in
glEvalCoord2 versions.
DESCRIPTION
glEvalCoord1 evaluates enabled one-dimensional maps at argu-
ment u. glEvalCoord2 does the same for two-dimensional maps
using two domain values, u and v. To define a map, call
glMap1 and glMap2; to enable and disable it, call glEnable
and glDisable.
When one of the glEvalCoord commands is issued, all
currently enabled maps of the indicated dimension are
evaluated. Then, for each enabled map, it is as if the
corresponding GL command had been issued with the computed
value. That is, if GL_MAP1_INDEX or GL_MAP2_INDEX is
enabled, a glIndex command is simulated. If GL_MAP1_COLOR_4
or GL_MAP2_COLOR_4 is enabled, a glColor command is
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simulated. If GL_MAP1_NORMAL or GL_MAP2_NORMAL is enabled, a
normal vector is produced, and if any of
GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2,
GL_MAP1_TEXTURE_COORD_3, GL_MAP1_TEXTURE_COORD_4,
GL_MAP2_TEXTURE_COORD_1, GL_MAP2_TEXTURE_COORD_2,
GL_MAP2_TEXTURE_COORD_3, or GL_MAP2_TEXTURE_COORD_4 is
enabled, then an appropriate glTexCoord command is simu-
lated.
For color, color index, normal, and texture coordinates the
GL uses evaluated values instead of current values for those
evaluations that are enabled, and current values otherwise,
However, the evaluated values do not update the current
values. Thus, if glVertex commands are interspersed with
glEvalCoord commands, the color, normal, and texture coordi-
nates associated with the glVertex commands are not affected
by the values generated by the glEvalCoord commands, but
only by the most recent glColor, glIndex, glNormal, and
glTexCoord commands.
No commands are issued for maps that are not enabled. If
more than one texture evaluation is enabled for a particular
dimension (for example, GL_MAP2_TEXTURE_COORD_1 and
GL_MAP2_TEXTURE_COORD_2), then only the evaluation of the
map that produces the larger number of coordinates (in this
case, GL_MAP2_TEXTURE_COORD_2) is carried out.
GL_MAP1_VERTEX_4 overrides GL_MAP1_VERTEX_3, and
GL_MAP2_VERTEX_4 overrides GL_MAP2_VERTEX_3, in the same
manner. If neither a three- nor a four-component vertex map
is enabled for the specified dimension, the glEvalCoord com-
mand is ignored.
If you have enabled automatic normal generation, by calling
glEnable with argument GL_AUTO_NORMAL, glEvalCoord2 gen-
erates surface normals analytically, regardless of the con-
tents or enabling of the GL_MAP2_N`_O_RMAL map. Let
`__ x `v
Then the generated normal n `is_____
n = ||m||
If automatic normal generation is disabled, the correspond-
ing normal map GL_MAP2_NORMAL, if enabled, is used to pro-
duce a normal. If neither automatic normal generation nor a
normal map is enabled, no normal is generated for
glEvalCoord2 commands.
ASSOCIATED GETS
glIsEnabled with argument GL_MAP1_VERTEX_3
glIsEnabled with argument GL_MAP1_VERTEX_4
glIsEnabled with argument GL_MAP1_INDEX
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glIsEnabled with argument GL_MAP1_COLOR_4
glIsEnabled with argument GL_MAP1_NORMAL
glIsEnabled with argument GL_MAP1_TEXTURE_COORD_1
glIsEnabled with argument GL_MAP1_TEXTURE_COORD_2
glIsEnabled with argument GL_MAP1_TEXTURE_COORD_3
glIsEnabled with argument GL_MAP1_TEXTURE_COORD_4
glIsEnabled with argument GL_MAP2_VERTEX_3
glIsEnabled with argument GL_MAP2_VERTEX_4
glIsEnabled with argument GL_MAP2_INDEX
glIsEnabled with argument GL_MAP2_COLOR_4
glIsEnabled with argument GL_MAP2_NORMAL
glIsEnabled with argument GL_MAP2_TEXTURE_COORD_1
glIsEnabled with argument GL_MAP2_TEXTURE_COORD_2
glIsEnabled with argument GL_MAP2_TEXTURE_COORD_3
glIsEnabled with argument GL_MAP2_TEXTURE_COORD_4
glIsEnabled with argument GL_AUTO_NORMAL
glGetMap
SEE ALSO
glBegin(3G), glColor(3G), glEnable(3G), glEvalMesh(3G),
glEvalPoint(3G), glIndex(3G), glMap1(3G), glMap2(3G),
glMapGrid(3G), glNormal(3G), glTexCoord(3G), glVertex(3G)
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