The glEvalPoint1 and glEvalPoint2 functions generate and evaluate a single point in a mesh.
void glEvalPoint1( GLint i ); void glEvalPoint2( GLint i, GLint j );
- The integer value for grid domain variable i.
- The integer value for grid domain variable j (glEvalPoint2 only).
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);
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
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.