Name

glEvalPoint — generate and evaluate a single point in a mesh

C Specification

void glEvalPoint1(GLint i);
 
void glEvalPoint2(GLint i,
 GLint j);
 

Parameters

i

Specifies the integer value for grid domain variable i.

j

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

Description

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
     	                  ·
     	                  Δ
     	                  u
     	              
     	              +
     	              
     	                  u
     	                  1
     	              
     	          
               );
         

where

Δ u = u 2 - u 1 n

and n, u 1 , and u 2 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 · Δ u + u 1 is exactly u 2 .

In the two-dimensional case, glEvalPoint2, let

Δ u = u 2 - u 1 n

Δ v = v 2 - v 1 m

where n, u 1 , u 2 , m, v 1 , and v 2 are the arguments to the most recent glMapGrid2 command. Then the glEvalPoint2 command is equivalent to calling

glEvalCoord2( 
			
		        
			    
			        i
				·
			        Δ
		                u
			    
		            +
		            
		                u
		                1
		            
			    ,
			    
			    
			        j
				·
			        Δ
		                v

			    
		            +
		            
		                v
		                1
		            
			
		     );
            

The only absolute numeric requirements are that if i = n , then the value computed from i · Δ u + u 1 is exactly u 2 , and if j = m , then the value computed from j · Δ v + v 1 is exactly v 2 .

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

See Also

glEvalCoord, glEvalMesh, glMap1, glMap2, glMapGrid

Copyright

Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.