glEvalCoord(3G)glEvalCoord(3G)NAME
glEvalCoord, glEvalCoord1d, glEvalCoord1f, glEvalCoord2d, glEvalCo‐
ord2f, glEvalCoord1dv, glEvalCoord1fv, glEvalCoord2dv, glEvalCoord2fv -
evaluate enabled one- and two-dimensional maps
SYNOPSIS
void glEvalCoord1d(
GLdouble u ); void glEvalCoord1f(
GLfloat u ); void glEvalCoord2d(
GLdouble u,
GLdouble v ); void glEvalCoord2f(
GLfloat u,
GLfloat v );
PARAMETERS
Specifies a value that is the domain coordinate u to the basis function
defined in a previous glMap1 or glMap2 command. 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 com‐
mand.
SYNOPSIS
void glEvalCoord1dv(
const GLdouble *u ); void glEvalCoord1fv(
const GLfloat *u ); void glEvalCoord2dv(
const GLdouble *u ); void glEvalCoord2fv(
const GLfloat *u );
PARAMETERS
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.
DESCRIPTIONglEvalCoord1() evaluates enabled one-dimensional maps at argument 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 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_TEX‐
TURE_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_TEX‐
TURE_COORD_4 is enabled, then an appropriate glTexCoord() command is
simulated.
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 val‐
ues do not update the current values. Thus, if glVertex() commands are
interspersed with glEvalCoord() commands, the color, normal, and tex‐
ture coordinates 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 glTexCo‐
ord() 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_VER‐
TEX_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 glE‐
valCoord() command is ignored.
If you have enabled automatic normal generation, by calling glEnable()
with argument GL_AUTO_NORMAL, glEvalCoord2() generates surface normals
analytically, regardless of the contents or enabling of the
GL_MAP2_NORMAL map. Let
dp du m = -- x --
du dv
Then the generated normal n is n = m
||m||
If automatic normal generation is disabled, the corresponding normal
map GL_MAP2_NORMAL, if enabled, is used to produce a normal. If neither
automatic normal generation nor a normal map is enabled, no normal is
generated for glEvalCoord2() commands.
ASSOCIATED GETSglIsEnabled() with argument GL_MAP1_VERTEX_3
glIsEnabled() with argument GL_MAP1_VERTEX_4
glIsEnabled() with argument GL_MAP1_INDEX
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 ALSOglBegin(3), glColor(3), glEnable(3), glEvalMesh(3), glEvalPoint(3),
glIndex(3), glMap1(3), glMap2(3), glMapGrid(3), glNormal(3), glTexCo‐
ord(3), glVertex(3)glEvalCoord(3G)