Gl.EvalPoint2 (gb.opengl)

Generate and evaluate a single point in a mesh.

Parameters

i

Specifies the integer value for grid domain variable $\mathit{i}$.

j

Specifies the integer value for grid domain variable $\mathit{j}$ (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( $\mathrm{i}·\Delta \mathit{u}+{\mathit{u}}_1$ );

where

and $\mathit{n}$, ${\mathit{u}}_1$, and ${\mathit{u}}_2$ are the arguments to the most recent Gl.MapGrid1 command. The one absolute numeric requirement is that if $\mathit{i}<code\; style="white-space:nowrap;"></code>\; <mi\; mathvariant="italic">n</mi>$, then the value computed from $\mathit{i}·\Delta \mathit{u}+{\mathit{u}}_1$ is exactly ${\mathit{u}}_2$.

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

where $\mathit{n}$, ${\mathit{u}}_1$, ${\mathit{u}}_2$, $\mathit{m}$, ${\mathit{v}}_1$, and ${\mathit{v}}_2$ are the arguments to the most recent Gl.MapGrid2 command. Then the Gl.EvalPoint2 command is equivalent to calling

glEvalCoord2( $\mathrm{i}·\Delta \mathit{u}+{\mathit{u}}_1,\mathrm{j}·\Delta \mathit{v}+{\mathit{v}}_1$ );

The only absolute numeric requirements are that if $\mathit{i}<code\; style="white-space:nowrap;"></code>\; <mi\; mathvariant="italic">n</mi>$, then the value computed from $\mathit{i}·\Delta \mathit{u}+{\mathit{u}}_1$ is exactly ${\mathit{u}}_2$, and if $\mathit{j}<code\; style="white-space:nowrap;"></code>\; <mi\; mathvariant="italic">m</mi>$, then the value computed from $\mathit{j}·\Delta \mathit{v}+{\mathit{v}}_1$ is exactly ${\mathit{v}}_2$.

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

See original documentation on OpenGL website