NAME
	  glMapGrid1d, glMapGrid1f, glMapGrid2d, glMapGrid2f - define
	  a one- or two-dimensional mesh


     C SPECIFICATION
	  void glMapGrid1d( GLint un,
			    GLdouble u1,
			    GLdouble u2	)
	  void glMapGrid1f( GLint un,
			    GLfloat u1,
			    GLfloat u2 )
	  void glMapGrid2d( GLint un,
			    GLdouble u1,
			    GLdouble u2,
			    GLint vn,
			    GLdouble v1,
			    GLdouble v2	)
	  void glMapGrid2f( GLint un,
			    GLfloat u1,
			    GLfloat u2,
			    GLint vn,
			    GLfloat v1,
			    GLfloat v2 )


     PARAMETERS
	  un  Specifies	the number of partitions in the	grid range
	      interval [u1, u2].  Must be positive.

	  u1, u2
	      Specify the mappings for integer grid domain values i=0
	      and i=un.

	  vn  Specifies	the number of partitions in the	grid range
	      interval [v1, v2]
	      (glMapGrid2 only).

	  v1, v2
	      Specify the mappings for integer grid domain values j=0
	      and j=vn
	      (glMapGrid2 only).

     DESCRIPTION
	  glMapGrid and	glEvalMesh are used together to	efficiently
	  generate and evaluate	a series of evenly-spaced map domain
	  values.  glEvalMesh steps through the	integer	domain of a
	  one- or two-dimensional grid,	whose range is the domain of
	  the evaluation maps specified	by glMap1 and glMap2.

	  glMapGrid1 and glMapGrid2 specify the	linear grid mappings
	  between the i	(or i and j) integer grid coordinates, to the
	  u (or	u and v) floating-point	evaluation map coordinates.
	  See glMap1 and glMap2	for details of how u and v coordinates
	  are evaluated.

	  glMapGrid1 specifies a single	linear mapping such that
	  integer grid coordinate 0 maps exactly to u1,	and integer
	  grid coordinate un maps exactly to u2.  All other integer
	  grid coordinates i are mapped	so that

			      u	= i(u2-u1)/un +	u1

	  glMapGrid2 specifies two such	linear mappings.  One maps
	  integer grid coordinate i=0 exactly to u1, and integer grid
	  coordinate i=un exactly to u2.  The other maps integer grid
	  coordinate j=0 exactly to v1,	and integer grid coordinate
	  j=vn exactly to v2.  Other integer grid coordinates i	and j
	  are mapped such that

			      u	= i(u2-u1)/un +	u1

			      v	= j(v2-v1)/vn +	v1

	  The mappings specified by glMapGrid are used identically by
	  glEvalMesh and glEvalPoint.

     ERRORS
	  GL_INVALID_VALUE is generated	if either un or	vn is not
	  positive.

	  GL_INVALID_OPERATION is generated if glMapGrid is executed
	  between the execution	of glBegin and the corresponding
	  execution of glEnd.

     ASSOCIATED	GETS
	  glGet	with argument GL_MAP1_GRID_DOMAIN
	  glGet	with argument GL_MAP2_GRID_DOMAIN
	  glGet	with argument GL_MAP1_GRID_SEGMENTS
	  glGet	with argument GL_MAP2_GRID_SEGMENTS

     SEE ALSO
	  glEvalCoord, glEvalMesh, glEvalPoint,	glMap1,	glMap2