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glMapGrid

Chapter 11

284

glMapGrid1 and glMapGrid2 specify the linear grid mappings between the i (or i and j)

integer grid coordinates, to the u (or u and v) ﬂoating-point evaluation map coordinates.

See glMap1 and glMap2 for details of how u and v coordinates are evaluated.

glMapGrid1 speciﬁes a single linear mapping such that integer grid coordinate 0 maps

exactly to u1, and integer grid coordinate un maps exactly to u2. All other integer grid

coordinates i are mapped so that

u = i (u2 u1) / un + u1

glMapGrid2 speciﬁes two such linear mappings. One maps integer grid coordinate i=0

exactly to u1, and integer grid coordinate i=un exactly to u2. The other maps integer grid

coordinate j=0 exactly to v1, and integer grid coordinate j=vn exactly to v2. Other integer

grid coordinates i and j are mapped such that

u = i (u2 u1) / un + u1

v = j (v2 v1) / vn + v1

The mappings speciﬁed by glMapGrid are used identically by glEvalMesh and

glEvalPoint.

Errors

• GL_INVALID_VALUE is generated if either un or vn is not positive.

• GL_INVALID_OPERATION is generated if glMapGrid is executed between the

execution of glBegin and the corresponding execution of glEnd.

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

HP b2600 Reference Guide

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