GLEVALPOINT(3G) GLEVALPOINT(3G)

glEvalPoint1, glEvalPoint2 - generate and evaluate a single point in a mesh

void glEvalPoint1( GLint i )



void glEvalPoint2( GLint i,


	GLint j )











  

  
Specifies the integer value for grid domain variable i.

  

  
Specifies the integer value for grid domain variable j
      (glEvalPoint2 only).










glMapGrid and glEvalMesh 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 gridspace that is traversed by glEvalMesh. Calling
    glEvalPoint1 is equivalent to calling



  

  

    
glEvalCoord1( i dot DELTA(u) + u1 );


  









where



  

  DELTA(u) = ( u2 - u1 ) / n
  






and n, u1, and u2 are the arguments to the most recent
    glMapGrid1 command. The one absolute numeric requirement is that if
    i=n, then the value computed from i dot 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 command. Then the glEvalPoint2 command is
    equivalent to calling



  

  

    
glEvalCoord2( i dot DELTA(u) + u1, j dot DELTA(v) + v1 );


  








The only absolute numeric requirements are that if i=n, then the value computed
  from i dot DELTA(u) + u1 is exactly u2, and if j=m, then the value computed
  from i dot DELTA(v) + v1 is exactly v2.







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








glEvalCoord, glEvalMesh, glMap1,
    glMap2, glMapGrid