# GLEVALPOINT

Section: Misc. Reference Manual Pages (3G)
Page Index

## NAME

glEvalPoint1, glEvalPoint2 - generate and evaluate a single point in a mesh

## C SPECIFICATION

void glEvalPoint1( GLint i )

void glEvalPoint2(
GLint i,
```
GLint j )
```

delim \$\$

## PARAMETERS

i
Specifies the integer value for grid domain variable \$i\$.
j
Specifies the integer value for grid domain variable \$j\$ (glEvalPoint2 only).

## DESCRIPTION

glMapGrid and glEvalMesh 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 glEvalMesh. Calling glEvalPoint1 is equivalent to calling
```

glEvalCoord1( i\$^cdot^DELTA u ~+~ u sub 1\$ );

```
where

\$DELTA u ~=~ ( u sub 2 - u sub 1 ) ^/^ n\$

and \$n\$, \$u sub 1\$, and \$u sub 2\$ are the arguments to the most recent glMapGrid1 command. The one absolute numeric requirement is that if \$i~=~n\$, then the value computed from \$i ^cdot^ DELTA u ~+~ u sub 1\$ is exactly \$u sub 2\$.

In the two-dimensional case, glEvalPoint2, let

```
\$DELTA u ~=~ mark ( u sub 2 - u sub 1 ) ^/^ n\$

\$DELTA v ~=~ mark ( v sub 2 - v sub 1 ) ^/^ m,\$
```

where \$n\$, \$u sub 1\$, \$u sub 2\$, \$m\$, \$v sub 1\$, and \$v sub 2\$ are the arguments to the most recent glMapGrid2 command. Then the glEvalPoint2 command is equivalent to calling

```

glEvalCoord2( i\$^cdot^DELTA u ~+~ u sub 1\$, j\$^cdot^DELTA v ~+~ v sub 1\$ );

```
The only absolute numeric requirements are that if \$i~=~n\$, then the value computed from \$i ^cdot^DELTA u ~+~ u sub 1\$ is exactly \$u sub 2\$, and if \$j~=~m\$, then the value computed from \$i ^cdot^DELTA v ~+~ v sub 1\$ is exactly \$v sub 2\$.

## ASSOCIATED GETS

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

glEvalCoord(3G), glEvalMesh(3G), glMap1(3G), glMap2(3G), glMapGrid(3G)

NAME
C SPECIFICATION
PARAMETERS
DESCRIPTION
ASSOCIATED GETS