glMapGrid.3gl

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 in tandem 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 such 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 called between a call to
  glBegin and the corresponding	call to	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

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Last Edited: Fri Dec 6 11:18:03 EST 1996 by AFV
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