Gl.EvalPoint1 (gb.opengl)

Static Sub EvalPoint1 ( I As Integer )

Generate and evaluate a single point in a mesh.

Parameters

i

Specifies the integer value for grid domain variable i.
j

Specifies the integer value for grid domain variable j (Gl.EvalPoint2 only).

Description

Gl.MapGrid and Gl.EvalMesh are used in tandem to efficiently generate and evaluate a series of evenly spaced map domain values. Gl.EvalPoint can be used to evaluate a single grid point in the same gridspace that is traversed by Gl.EvalMesh. Calling Gl.EvalPoint1 is equivalent to calling
glEvalCoord1( 


i
·
Δ
u

+

u
1


 );

where Δ u u 2 - u 1 n

and n, u 1 , and u 2 are the arguments to the most recent Gl.MapGrid1 command. The one absolute numeric requirement is that if i n , then the value computed from i · Δ u + u 1 is exactly u 2 .

In the two-dimensional case, Gl.EvalPoint2, let

Δ u u 2 - u 1 n

Δ v v 2 - v 1 m

where n, u 1 , u 2 , m, v 1 , and v 2 are the arguments to the most recent Gl.MapGrid2 command. Then the Gl.EvalPoint2 command is equivalent to calling
glEvalCoord2( 


i
·
Δ
u

+

u
1

,

j
·
Δ
v

+

v
1


 );

The only absolute numeric requirements are that if i n , then the value computed from i · Δ u + u 1 is exactly u 2 , and if j m , then the value computed from j · Δ v + v 1 is exactly v 2 .

Associated Gets

Gl.Get with argument Gl.MAP1_GRID_DOMAIN

Gl.Get with argument Gl.MAP2_GRID_DOMAIN

Gl.Get with argument Gl.MAP1_GRID_SEGMENTS

Gl.Get with argument Gl.MAP2_GRID_SEGMENTS

See also

Gl.EvalCoord, Gl.EvalMesh, Gl.Map1, Gl.Map2, Gl.MapGrid

See original documentation on OpenGL website