glEvalPoint1, glEvalPoint2

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

void glEvalPoint1(
  GLint i
);

void glEvalPoint2(
  GLint i,
  GLint j
);

Parameters

i
The integer value for grid domain variable i.
j
The integer value for grid domain variable j (glEvalPoint2 only).

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(iΔu + u1);

where

Δu = (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 iΔ u + u1 is exactly u2.

In the two-dimensional case, glEvalPoint2, let

Δu = (u2 u1)/n

Δv = (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(iΔu + u1, jΔv + v1);

The only absolute numeric requirements are that if i = n, then the value computed from iΔu + u1 is exactly u2, and if j = m, then the value computed from jΔv + 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

  Windows NT/2000: Requires Windows NT 3.5 or later.
  Windows 95/98: Requires Windows 95 or later. Available as a redistributable for Windows 95.
  Header: Declared in Gl.h.
  Library: Use Opengl32.lib.

See Also

glEvalCoord, glEvalMesh, glGet, glMap1, glMap2, glMapGrid


  

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