GLMAPGRID

Section: Misc. Reference Manual Pages (3G)
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NAME

glMapGrid1d, glMapGrid1f, glMapGrid2d, glMapGrid2f - define a one- or two-dimensional mesh

C SPECIFICATION

void glMapGrid1d( GLint un,


                    GLdouble u1,
                    GLdouble u2 )

void glMapGrid1f( GLint un,


                    GLfloat u1,
                    GLfloat u2 )

void glMapGrid2d( GLint un,


                    GLdouble u1,
                    GLdouble u2,
                    GLint vn,
                    GLdouble v1,
                    GLdouble v2 )

void glMapGrid2f( GLint un,


                    GLfloat u1,
                    GLfloat u2,
                    GLint vn,
                    GLfloat v1,
                    GLfloat v2 )

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PARAMETERS

un: Specifies the number of partitions in the grid range interval [u1, u2]. Must be positive.
u1, u2: Specify the mappings for integer grid domain values $i~=~0$ and $i~=~"un"$.
vn: Specifies the number of partitions in the grid range interval [v1, v2]
(glMapGrid2 only).
v1, v2: Specify the mappings for integer grid domain values $j~=~0$ and $j~=~"vn"$
(glMapGrid2 only).

DESCRIPTION

glMapGrid and glEvalMesh are used together to efficiently generate and evaluate a series of evenly-spaced map domain values. glEvalMesh steps through the integer domain of a one- or two-dimensional grid, whose range is the domain of the evaluation maps specified by glMap1 and glMap2.

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