MirOS Manual: glEvalCoord(3), glEvalCoord1d(3), glEvalCoord1dv(3), glEvalCoord1fv(3), glEvalCoord2d(3), glEvalCoord2dv(3), glEvalCoord2f(3), glEvalCoord2fv(3)


GLEVALCOORD(3G)     UNIX Programmer's Manual      GLEVALCOORD(3G)

NAME

     glEvalCoord1d, glEvalCoord1f, glEvalCoord2d, glEvalCoord2f,
     glEvalCoord1dv, 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 versions.

DESCRIPTION

     glEvalCoord1 evaluates enabled one-dimensional maps at argu-
     ment 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

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GLEVALCOORD(3G)     UNIX Programmer's Manual      GLEVALCOORD(3G)

     simulated. If GL_MAP1_NORMAL or GL_MAP2_NORMAL is enabled, 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 command is simu-
     lated.

     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 values do not update the current
     values. Thus, if glVertex commands are interspersed with
     glEvalCoord commands, the color, normal, and texture coordi-
     nates 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 dimension, the glEvalCoord com-
     mand is ignored.

     If you have enabled automatic normal generation, by calling
     glEnable with argument GL_AUTO_NORMAL, glEvalCoord2 gen-
     erates surface normals analytically, regardless of the con-
     tents or enabling of the GL_MAP2_N`_O_RMAL map. Let
                                 `__ x `v
     Then the generated normal n `is_____
                              n = ||m||
     If automatic normal generation is disabled, the correspond-
     ing normal map GL_MAP2_NORMAL, if enabled, is used to pro-
     duce a normal. If neither automatic 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

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     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)

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