Method GL.glEvalPoint()

Method glEvalPoint

void glEvalPoint(int|array(int) i, int|void j)

Description

glMapGrid and glEvalMesh1 and glEvalMesh2 are used in tandem to efficiently generate and evaluate a series of evenly spaced map domain values. glEvalPoint can be used to evaluate a single grid point in the same gridspace that is traversed by glEvalMesh1 and glEvalMesh2. Calling glEvalPoint is equivalent to calling

glEvalCoord1( i·Δu+u1 );

where Δu=(u₂-u₁)/n

and n, u₁, and u₂ are the arguments to the most recent glMapGrid command. The one absolute numeric requirement is that if i=n , then the value computed from i·Δu+u₁ is exactly u₂.

In the two-dimensional case, glEvalPoint, let

Δu=(u₂-u₁)/n Δv=(v₂-v₁)/m

where n, u₁, u₂, m, v₁, and v₂ are the arguments to the most recent glMapGrid command. Then the glEvalPoint command is equivalent to calling

glEvalCoord2( i·Δu+u1,j·Δv+v1 );

The only absolute numeric requirements are that if i=n , then the value computed from i·Δu+u₁ is exactly u₂, and if j=m , then the value computed from j·Δv+v₁ is exactly v₂.

Parameter i

Specifies the integer value for grid domain variable i.

Parameter j

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