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 glMatrixMode) is multiplied by this matrix  and
       the  result replaces the current matrix, as if glMultMatrix 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)

       execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

       glGet with argument GL_MATRIX_MODE
       glGet with argument GL_COLOR_MATRIX
       glGet with argument GL_MODELVIEW_MATRIX
       glGet with argument GL_PROJECTION_MATRIX
       glGet with argument GL_TEXTURE_MATRIX

SEE ALSO

       glFrustum, glMatrixMode, glMultMatrix, glPushMatrix, glViewport



                                                                   GLORTHO(3G)