GLORTHO(3G)                                                        GLORTHO(3G)



NAME
       glOrtho - multiply the current matrix with an orthographic matrix


C SPECIFICATION
       void glOrtho( GLdouble left,
                     GLdouble right,
                     GLdouble bottom,
                     GLdouble top,
                     GLdouble zNear,
                     GLdouble zFar )


PARAMETERS
       left, right Specify  the  coordinates  for  the left and right vertical
                   clipping planes.

       bottom, top Specify the coordinates for the bottom and  top  horizontal
                   clipping planes.

       zNear, zFar Specify the distances to the nearer and farther depth clip-
                   ping planes.  These values are negative if the plane is  to
                   be behind the viewer.

DESCRIPTION
       glOrtho describes a transformation that produces a parallel projection.
       The current matrix (see glatrixode) is multiplied by this matrix  and
       the  result replaces the current matrix, as if glultatrix were called
       with the following matrix as its argument:



              2
        ------------       0              0              tx
        right - left

                           2
            0         ------------        0              ty
                      top - bottom


                                          -2
            0              0         ------------        tz
                                      zFar-zNear

            0              0              0              1


       where

                       tx = - (right ] left) / (right - left)

                       ty = - (top ] bottom) / (top - bottom)

                       tz = - (zFar ] zNear) / (zFar - zNear)


       Typically,  the  matrix  mode  is  GLPROJECTION,  and  (left,  bottom,
       -zNear)  and (right, top,  -zNear) specify the points on the near clip-
       ping plane that are mapped to the lower left and upper right corners of
       the  window,  respectively,  assuming that the eye is located at (0, 0,
       0).  -zFar specifies the location of  the  far  clipping  plane.   Both
       zNear and zFar can be either positive or negative.

       Use glPushatrix and glPopatrix to save and restore the current matrix
       stack.

ERORS
       GLINVALIDOPERATION is generated if glOrtho is  executed  between  the
       execution of glBegin and the corresponding execution of glEnd.

ASOCIATED GETS
       glGet with argument GLMATRIXMODE
       glGet with argument GLCOLORMATRIX
       glGet with argument GLMODELVIEWMATRIX
       glGet with argument GLPROJECTIONMATRIX
       glGet with argument GLTEXTUREMATRIX

SEE ALSO
       glFrustum, glatrixode, glultatrix, glPushatrix, glViewport



                                                                   GLORTHO(3G)