glEvalCoord1fv man page on DigitalUNIX

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glEvalCoord(3G)						       glEvalCoord(3G)

       glEvalCoord,  glEvalCoord1d,  glEvalCoord1f,  glEvalCoord2d,  glEvalCo‐
       ord2f, glEvalCoord1dv, glEvalCoord1fv, glEvalCoord2dv, glEvalCoord2fv -
       evaluate enabled one- and two-dimensional maps

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

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

       void glEvalCoord1dv(
	       const GLdouble *u ); void glEvalCoord1fv(
	       const GLfloat *u ); void glEvalCoord2dv(
	       const GLdouble *u ); void glEvalCoord2fv(
	       const GLfloat *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() versions.

       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 produced, and if  any  of
       TURE_COORD_4 is enabled, then an appropriate  glTexCoord()  command  is

       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 tex‐
       ture 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  glTexCo‐
       ord() 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_VER‐
       TEX_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 dimension,  the  glE‐
       valCoord() 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
	   dp	du m = -- x --
	   du	dv

       Then the generated normal n is n =  m

       If automatic normal generation is disabled,  the	 corresponding	normal
       map GL_MAP2_NORMAL, if enabled, is used to produce a normal. If neither
       automatic normal generation nor a normal map is enabled, no  normal  is
       generated for glEvalCoord2() commands.

       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

       glBegin(3),  glColor(3),	 glEnable(3),  glEvalMesh(3),  glEvalPoint(3),
       glIndex(3), glMap1(3), glMap2(3), glMapGrid(3),	glNormal(3),  glTexCo‐
       ord(3), glVertex(3)


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