glMapGrid1d, glMapGrid1f, glMapGrid2d, glMapGrid2f
These functions define a one- or two-dimensional mesh.
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);
Parameters
- un
The number of partitions in the grid range interval [u1, u2]. Must be positive. - u1, u2
The mappings for integer grid domain values *i *= 0 and *i *= un. - vn
The number of partitions in the grid range interval [v1, v2] (glMapGrid2 only). - v1, v2
The mappings for integer grid domain values j = 0 and j = vn (glMapGrid2 only).
Remarks
The glMapGrid and glEvalMesh functions are used in tandem to efficiently generate and evaluate a series of evenly spaced map domain values. The glEvalMesh function 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.
The glMapGrid1 and glMapGrid2 functions 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.
The glMapGrid1 function 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 such that:
u = i(u2 u1)/un + u1
The glMapGrid2 function 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.
The following functions retrieve information related to glMapGrid:
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
Error Codes
The following are the error codes generated and their conditions.
Error code | Condition |
---|---|
GL_INVALID_VALUE | Either un or vn was not positive. |
GL_INVALID_OPERATION | glMapGrid was called between a call to glBegin and the corresponding call to glEnd. |
Requirements
** Windows NT/2000:** Requires Windows NT 3.5 or later.
** Windows 95/98:** Requires Windows 95 or later. Available as a redistributable for Windows 95.
** Header:** Declared in Gl.h.
** Library:** Use Opengl32.lib.
See Also
glBegin, glEnd, glEvalCoord, glEvalMesh, glEvalPoint, glMap1, glMap2