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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 clipping 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)


       Typically, the matrix mode is GL_PROJECTION, and (left, bottom,  -zNear) and  (right,  top,   -zNear)
       specify  the points on the near clipping plane that are mapped to the lower left and upper right cor-ners corners
       ners 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 glPushMatrix and glPopMatrix to save and restore the current matrix stack.

ERRORS
       GL_INVALID_OPERATION  is  generated  if  glOrtho is executed between the 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(3G), glMatrixMode(3G), glMultMatrix(3G), glPushMatrix(3G), glViewport(3G)




                                                                                                 GLORTHO(3G)