glMapGrid Subroutine

OpenGL 1.1 for AIX: Reference Manual

glMapGrid Subroutine

Purpose

Defines a 1-dimensional (1D) or 2-dimensional (2D) mesh.

Library

OpenGL C bindings library: libGL.a

C Syntax

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

The glMapGrid and glEvalMesh subroutines are used in tandem to efficiently generate and evaluate a series of evenly spaced map domain values. The glEvalMesh subroutine steps through the integer domain of a 1D or 2D grid, whose range is the domain of the evaluation maps specified by the glMap1 and glMap2 subroutines.

The glMapGrid1 and glMapGrid2 subroutines 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 the glMap1 subroutine and the glMap2 subroutine for details of how u and v coordinates are evaluated.

The glMapGrid1 subroutine specifies a single linear mapping such that integer grid coordinate 0 (zero) 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

The glMapGrid2 subroutine 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 identically used by glEvalMesh and glEvalPoint.

Errors

GL_INVALID_VALUE	un or vn is not positive.
GL_INVALID_OPERATION	The glMapGrid subroutine is called between a call to glBegin and the corresponding call to glEnd.

Associated Gets

Associated gets for the glMapGrid subroutine are as follows. (See the glGet subroutine for more information.)

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.

Files

/usr/include/GL/gl.h

Contains C language constants, variable type definitions, and ANSI function prototypes for OpenGL.

Related Information

The glBegin or glEnd subroutine, glEvalCoord subroutine, glEvalMesh subroutine, glEvalPoint subroutine, glMap1 subroutine, glMap2 subroutine.

OpenGL Overview.