GLEVALCOORD() GLEVALCOORD() NAME glEvalCoord1d, glEvalCoord1f, glEvalCoord2d, glEvalCoord2f, glEvalCoord1dv, glEvalCoord1fv, glEvalCoord2dv, glEvalCoord2fv - evaluate enabled one- and two-dimensional maps delim $$ 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 func- tion defined in a previous glMap1 or glMap2 command. v Specifies a value that is the domain coordinate $v$ to the basis func- tion 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 versions. DESCRIPTION glEvalCoord1 evaluates enabled one-dimensional maps at argument u. glEval- Coord2 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 en- abled, a normal vector is produced, 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 com- mand is simulated. For color, color index, normal, and texture coordinates the GL uses evalu- ated values instead of current values for those evaluations that are en- abled, and current values otherwise, However, the evaluated values do not update the current values. Thus, if glVertex commands are interspersed with glEvalCoord commands, the color, normal, and texture coordinates asso- ciated 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 evalua- tion 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 en- abled for the specified dimension, the glEvalCoord command is ignored. If you have enabled automatic normal generation, by calling glEnable with argument GL_AUTO_NORMAL, glEvalCoord2 generates surface normals analyti- cally, regardless of the contents or enabling of the GL_MAP2_NORMAL map. Let Pp Pp m = -- X -- Pu Pv Then the generated normal $ n $ is $n = m over ~ over { || m || }$ If automatic normal generation is disabled, the corresponding normal map GL_MAP2_NORMAL, if enabled, is used to produce a normal. If neither auto- matic normal generation nor a normal map is enabled, no normal 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, glColor, glEnable, glEvalMesh, glEvalPoint, glIndex, glMap1, glMap2, glMapGrid, glNormal, glTexCoord, glVertex GLEVALCOORD()
NAME | C SPECIFICATION | PARAMETERS | C SPECIFICATION | PARAMETERS | DESCRIPTION | ASSOCIATED GETS | SEE ALSO
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