glEvalPoint1 function

The glEvalPoint1 and glEvalPoint2 functions generate and evaluate a single point in a mesh.

Syntax

void glEvalPoint1(
   GLint i
);

Parameters

i

The integer value for grid ___domain variable i.

Return value

This function does not return a value.

Remarks

The glMapGrid and glEvalMesh functions are used in tandem to efficiently generate and evaluate a series of evenly spaced map ___domain values. You can use glEvalPoint to evaluate a single grid point in the same gridspace that is traversed by glEvalMesh. Calling glEvalPoint1 is equivalent to calling

glEvalCoord1 (i ?u +u1 );

where

?u = (u2 u1 )/n

and n, u1 , and u2 are the arguments to the most recent glMapGrid1 function. The one absolute numeric requirement is that if i = n, then the value computed from (i ?u + u1 ) is exactly u2 .

In the two-dimensional case, glEvalPoint2, let

?u = (u2 u1 )/n

?v = (v2 v1 )/m

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

glEvalCoord2 (i ?u + u1 , j ?v + v1 );

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

The following functions retrieve information relating to glEvalPoint1 and glEvalPoint2:

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

Requirements

See also

glEvalCoord

glEvalMesh

glGet

glMap1

glMap2

glMapGrid