Table of Contents

Name

glEvalCoord1d, glEvalCoord1f, glEvalCoord2d, glEvalCoord2f, glEvalCoord1dv, glEvalCoord1fv, glEvalCoord2dv, glEvalCoord2fv - evaluate enabled one- and

two-dimensional maps

eqn not supported

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 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_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 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 values do not update the current
values. Thus, if glVertex commands are interspersed with glEvalCoord commands,
the color, normal, and texture 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 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 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 


eqn not supported




Then the generated normal $ bold n $ is  


$bold n ~=~ bold m over { || bold m || }$



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 Gets




glIsEnabled 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(3G), glColor(3G), glEnable(3G), glEvalMesh(3G), glEvalPoint(3G),
glIndex(3G), glMap1(3G), glMap2(3G),  glMapGrid(3G), glNormal(3G), glTexCoord(3G),
glVertex(3G)