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OpenGL 1.2 for AIX: Reference Manual

glEvalPoint Subroutine

Purpose

Generates and evaluates a single point in a mesh.

Library

OpenGL C bindings library: libGL.a

C Syntax

void glEvalPoint1(GLint i)
void glEvalPoint2(GLint i,
   GLint j)

Description

The glMapGrid and glEvalMesh subroutines are used in tandem to efficiently generate and evaluate a series of evenly spaced map domain values. glEvalPoint can be used to evaluate a single grid point in the same grid space that is traversed by glEvalMesh. Calling glEvalPoint1 is equivalent to calling

EvalCoord1(i (DELTA u) + u1);

where DELTA u = (u2 - u1)/n and n, u1, and u2 are the arguments to the most recent glMapGrid1 subroutine. The one absolute numeric requirement is that if i = n, the value computed from i (DELTA u) + u1 is exactly u2.

In the two-dimensional case, glEvalPoint2, let

DELTA u = (u2 - u1 )/n
DELTA v = (v2 - v1 )/m

where n, u1, u2, m, v1, and v2 are the arguments to the most recent glMapGrid2 subroutine. Then the glEvalPoint2 subroutine is equivalent to calling:

EvalCoord2(i (DELTA u) + u1,
j (DELTA v) + v1)

The only absolute numeric requirements are that if i = n, the value computed from i (DELTA u) + u1 is exactly u2, and if j = m, the value computed from j (DELTA v) + v1 is exactly v2.

Parameters

i Specifies the integer value for grid domain variable i.
j Specifies the integer value for grid domain variable j. (This parameter applies to glEvalPoint2 only.)

Associated Gets

Associated gets for the glEvalPoint 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 glEvalCoord subroutine, glEvalMesh subroutine, glMap1 subroutine, glMap2 subroutine, glMapGrid subroutine.

OpenGL Overview.


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