glEvalMesh2 function
Computes a twodimensional grid of points or lines.
Syntax
void WINAPI glEvalMesh2(
GLenum mode,
GLint i1,
GLint i2,
GLint j1,
GLint j2
);
Parameters
 mode

A value that specifies whether to compute a twodimensional mesh of points, lines, or polygons. The following symbolic constants are accepted: GL_POINT, GL_LINE, and GL_FILL.
 i1

The first integer value for grid domain variable i.
 i2

The last integer value for grid domain variable i.
 j1

The first integer value for grid domain variable j.
 j2

The last integer value for grid domain variable j.
Return value
This function does not return a value.
Error codes
The following error codes can be retrieved by the glGetError function.
Name  Meaning 


Indicates that mode is not an accepted value. 

The function was called between a call to glBegin and the corresponding call to glEnd. 
Error codes
The following error codes can be retrieved by the glGetError function.
Name  Meaning 


Indicates that mode is not an accepted value. 

The function was called between a call to glBegin and the corresponding call to glEnd. 
Remarks
Use glMapGrid and glEvalMesh in tandem to efficiently generate and evaluate a series of evenly spaced map domain values. The glEvalMesh function steps through the integer domain of a one or twodimensional grid, whose range is the domain of the evaluation maps specified by glMap1 and glMap2. The mode parameter determines whether the resulting vertices are connected as points, lines, or filled polygons.
In the twodimensional case, glEvalMesh2, let
Δ u = (u₂ u₁)/n
Δ v = (v₂ v₁)/m,
where n, u₁, u₂, m, v₁, and v₂ are the arguments to the most recent glMapGrid2 function. Then, if mode is GL_FILL, glEvalMesh2 is equivalent to:
for (j = j1; j < j2; j += 1)
{
glBegin(GL_QUAD_STRIP);
for (i = i1; i <= i2; i += 1)
{
glEvalCoord2(iΔ u + u1 ( ) , j Δ v + v1);
glEvalCoord2(iΔ u + u1 ( ) , (j+1) Δ v + v1);
}
glEnd( ); }
If mode is GL_LINE, then a call to glEvalMesh2 is equivalent to:
for (j = j1; j <= j2; j += 1)
{
glBegin(GL_LINE_STRIP);
for (i = i1; i <= i2; i += 1)
{
glEvalCoord2(iΔ u + u1, jΔ v + v1);
}
glEnd( );
}
for (i = i1; i <= i2; i += 1)
{
glBegin(GL_LINE_STRIP);
for (j = j1; j <= j1; j += 1)
{
glEvalCoord2(iΔ u + u1, jΔ v + v1);
}
glEnd( );
}
And finally, if mode is GL_POINT, then a call to glEvalMesh2 is equivalent to:
glBegin(GL_POINTS);
for (j = j1; j <= j2; j += 1)
{
for (i = i1; i <= i2; i += 1)
{
glEvalCoord2(iΔ u + u1, jΔ v + v1);
}
}
glEnd( );
In all three cases, the only absolute numeric requirements are that if i = n, then the value computed from iΔ u + u₁ is exactly u₂, and if j = m, then the value computed from jΔ v + v₁ is exactly v₂. The following functions retrieve information relating to glEvalMesh:
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
Minimum supported client  Windows 2000 Professional [desktop apps only] 

Minimum supported server  Windows 2000 Server [desktop apps only] 
Header 

Library 

DLL 
