Gl.EvalPoint2 (gb.opengl)

Static Sub EvalPoint2 ( I As Integer, J 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(  $i \cdot Δ u + u_{1}$  );

where

Δ u \frac{(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 \cdot Δ u + u_{1}

is exactly

u_{2}

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

Δ u \frac{(u_{2} - u_{1})}{n}

Δ v \frac{(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(  $i \cdot Δ u + u_{1}, j \cdot Δ v + v_{1}$  );

The only absolute numeric requirements are that if

i n

, then the value computed from

i \cdot Δ u + u_{1}

is exactly

u_{2}

, and if

j m

, then the value computed from

j \cdot 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

Gl.EvalPoint2 (gb.opengl)

Parameters

Description

Associated Gets

See also