glMapGrid1d, glMapGrid1f, glMapGrid2d, glMapGrid2f

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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