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GLEVALCOORD(3G) 			  OpenGL Manual 			  GLEVALCOORD(3G)

NAME
       glEvalCoord - evaluate enabled one- and two-dimensional maps

C SPECIFICATION
       void glEvalCoord1f(GLfloat u);

       void glEvalCoord1d(GLdouble u);

       void glEvalCoord2f(GLfloat u, GLfloat v);

       void glEvalCoord2d(GLdouble u, GLdouble 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 glEvalCoord1fv(const GLfloat * u);

       void glEvalCoord1dv(const GLdouble * u);

       void glEvalCoord2fv(const GLfloat * u);

       void glEvalCoord2dv(const GLdouble * 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

       m = a p a u x a p a v

       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 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 ALSO
       glBegin(), glColor(), glEnable(), glEvalMesh(), glEvalPoint(), glIndex(), glMap1(),
       glMap2(), glMapGrid(), glNormal(), glTexCoord(), glVertex()

COPYRIGHT
       Copyright (C) 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI
       Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.

AUTHORS
       opengl.org

opengl.org				    06/10/2014				  GLEVALCOORD(3G)
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