Generates and evaluates a single point in a mesh.
OpenGL C bindings library: libGL.a
void glEvalPoint1(GLint i)
void glEvalPoint2(GLint i, GLint j)
| i | Specifies the integer value for grid domain variable i. |
| j | Specifies the integer value for grid domain variable j. (This parameter applies to glEvalPoint2 only.) |
The glMapGrid and glEvalMesh subroutines 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 grid space that is traversed by glEvalMesh. Calling glEvalPoint1 is equivalent to calling
EvalCoord1(i (DELTA u) + u1);
where DELTA u = (u2 - u1)/n and n, u1, and u2 are the arguments to the most recent glMapGrid1 subroutine. The one absolute numeric requirement is that if i = n, the value computed from i (DELTA u) + u1 is exactly u2.
In the two-dimensional case, glEvalPoint2, let
DELTA u = (u2 - u1 )/n DELTA v = (v2 - v1 )/m
where n, u1, u2, m, v1, and v2 are the arguments to the most recent glMapGrid2 subroutine. Then the glEvalPoint2 subroutine is equivalent to calling:
EvalCoord2(i (DELTA u) + u1, j (DELTA v) + v1)
The only absolute numeric requirements are that if i = n, the value computed from i (DELTA u) + u1 is exactly u2, and if j = m, the value computed from j (DELTA v) + v1 is exactly v2.
Associated gets for the glEvalPoint subroutine are as follows. (See the glGet subroutine for more information.)
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.
| /usr/include/GL/gl.h | Contains C language constants, variable type definitions, and ANSI function prototypes for OpenGL. |
The glEvalCoord subroutine, glEvalMesh subroutine, glMap1 subroutine, glMap2 subroutine, glMapGrid subroutine.