glEvalCoord2f

GLEVALCOORD(3G)						      GLEVALCOORD(3G)



NAME
       glEvalCoord1d,  glEvalCoord1f, glEvalCoord2d, glEvalCoord2f, glEvalCo-
       ord1dv,	glEvalCoord1fv,	 glEvalCoord2dv,  glEvalCoord2fv  -  evaluate
       enabled one- and two-dimensional maps


C SPECIFICATION
       void glEvalCoord1d( GLdouble u )
       void glEvalCoord1f( GLfloat u )
       void glEvalCoord2d( GLdouble u,
			   GLdouble v )
       void glEvalCoord2f( GLfloat u,
			   GLfloat v )


PARAMETERS
       u  Specifies  a	value  that  is	 the domain coordinate u to the basis
	  function defined in a previous glMap1 or glMap2 command.

       v  Specifies a value that is the domain	coordinate  v  to  the	basis
	  function  defined  in	 a previous glMap2 command.  This argument is
	  not present in a glEvalCoord1 command.

C SPECIFICATION
       void glEvalCoord1dv( const GLdouble *u )
       void glEvalCoord1fv( const GLfloat *u )
       void glEvalCoord2dv( const GLdouble *u )
       void glEvalCoord2fv( const GLfloat *u )


PARAMETERS
       u      Specifies a pointer to an array containing either	 one  or  two
	      domain  coordinates.   The  first	 coordinate is u.  The second
	      coordinate is v, which is present	 only  in  glEvalCoord2	 ver-
	      sions.

DESCRIPTION
       glEvalCoord1  evaluates	enabled	 one-dimensional  maps at argument u.
       glEvalCoord2 does the same for two-dimensional maps using  two  domain
       values,	u  and v.  To define a map, call glMap1 and glMap2; to enable
       and disable it, call glEnable and glDisable.

       When one of the glEvalCoord commands is issued, all currently  enabled
       maps of the indicated dimension are evaluated.  Then, for each enabled
       map, it is as if the corresponding GL command had been issued with the
       computed	 value.	  That	is,  if	 GL_MAP1_INDEX	or  GL_MAP2_INDEX  is
       enabled, a  glIndex  command  is	 simulated.   If  GL_MAP1_COLOR_4  or
       GL_MAP2_COLOR_4	is  enabled,  a	 glColor  command  is  simulated.  If
       GL_MAP1_NORMAL or GL_MAP2_NORMAL is enabled, a normal vector  is	 pro-
       duced, and if any of GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2,
       GL_MAP1_TEXTURE_COORD_3,			     GL_MAP1_TEXTURE_COORD_4,
       GL_MAP2_TEXTURE_COORD_1,			     GL_MAP2_TEXTURE_COORD_2,
       GL_MAP2_TEXTURE_COORD_3, or GL_MAP2_TEXTURE_COORD_4 is  enabled,	 then
       an appropriate glTexCoord command is simulated.

       For  color,  color  index, normal, and texture coordinates the GL uses
       evaluated values instead of current values for those evaluations	 that
       are enabled, and current values otherwise, However, the evaluated val-
       ues do not update the current values.  Thus, if glVertex commands  are
       interspersed with glEvalCoord commands, the color, normal, and texture
       coordinates associated with the glVertex commands are not affected  by
       the values generated by the glEvalCoord commands, but only by the most
       recent glColor, glIndex, glNormal, and glTexCoord commands.

       No commands are issued for maps that are not enabled.   If  more	 than
       one  texture  evaluation	 is  enabled  for a particular dimension (for
       example, GL_MAP2_TEXTURE_COORD_1	 and  GL_MAP2_TEXTURE_COORD_2),	 then
       only  the  evaluation  of  the  map that produces the larger number of
       coordinates (in this case, GL_MAP2_TEXTURE_COORD_2)  is	carried	 out.
       GL_MAP1_VERTEX_4	  overrides  GL_MAP1_VERTEX_3,	and  GL_MAP2_VERTEX_4
       overrides GL_MAP2_VERTEX_3, in the same manner.	If neither  a  three-
       nor  a  four-component  vertex map is enabled for the specified dimen-
       sion, the glEvalCoord command is ignored.

       If you have enabled automatic normal generation, by  calling  glEnable
       with  argument  GL_AUTO_NORMAL, glEvalCoord2 generates surface normals
       analytically,  regardless  of  the  contents  or	  enabling   of	  the
       GL_MAP2_NORMAL map.  Let

				      m=__×__

       Then the generated normal n is
				      n=_____

       If  automatic  normal generation is disabled, the corresponding normal
       map GL_MAP2_NORMAL, if enabled, is used to produce a normal.  If	 nei-
       ther  automatic normal generation nor a normal map is enabled, no nor-
       mal is generated for glEvalCoord2 commands.

ASSOCIATED GETS
       glIsEnabled with argument GL_MAP1_VERTEX_3
       glIsEnabled with argument GL_MAP1_VERTEX_4
       glIsEnabled with argument GL_MAP1_INDEX
       glIsEnabled with argument GL_MAP1_COLOR_4
       glIsEnabled with argument GL_MAP1_NORMAL
       glIsEnabled with argument GL_MAP1_TEXTURE_COORD_1
       glIsEnabled with argument GL_MAP1_TEXTURE_COORD_2
       glIsEnabled with argument GL_MAP1_TEXTURE_COORD_3
       glIsEnabled with argument GL_MAP1_TEXTURE_COORD_4
       glIsEnabled with argument GL_MAP2_VERTEX_3
       glIsEnabled with argument GL_MAP2_VERTEX_4
       glIsEnabled with argument GL_MAP2_INDEX
       glIsEnabled with argument GL_MAP2_COLOR_4
       glIsEnabled with argument GL_MAP2_NORMAL
       glIsEnabled with argument GL_MAP2_TEXTURE_COORD_1
       glIsEnabled with argument GL_MAP2_TEXTURE_COORD_2
       glIsEnabled with argument GL_MAP2_TEXTURE_COORD_3
       glIsEnabled with argument GL_MAP2_TEXTURE_COORD_4
       glIsEnabled with argument GL_AUTO_NORMAL
       glGetMap

SEE ALSO
       glBegin(3G),	 glColor(3G),	   glEnable(3G),      glEvalMesh(3G),
       glEvalPoint(3G),	 glIndex(3G),  glMap1(3G), glMap2(3G), glMapGrid(3G),
       glNormal(3G), glTexCoord(3G), glVertex(3G)



							      GLEVALCOORD(3G)