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OpenGL 1.1 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)

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.)

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.

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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