glOrtho(3)

NAME

       glOrtho - multiply the current matrix with an orthographic matrix

C SPECIFICATION

       void glOrtho( GLdouble left,
                     GLdouble right,
                     GLdouble bottom,
                     GLdouble top,
                     GLdouble near_val,
                     GLdouble far_val )

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.

       near_val, far_val
                   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:

                                  left (  matrix {
          ccol { {2 over {"right" - "left"}} above 0 above 0 above 0 }
          ccol { 0 above {2 over {"top" - "bottom"}} above 0 above 0 }
          ccol { 0 above 0 above {-2 over {"far_val" - "near_val"}}  above 0 }
          ccol  {  {t  sub  x}~ above {t sub y}~ above {t sub z}~ above 1~ } }
       right )

       where
           t sub x ~=~ -^{{"right" ~+~ "left"} over {"right" ~-~ "left"}}

           t sub y ~=~ -^{{"top" ~+~ "bottom"} over {"top" ~-~ "bottom"}}

       t sub z ~=~ -^{{"far_val" ~+~ "near_val"} over {"far_val" ~-~ "near_val"}}

Typically, the matrix mode is GL_PROJECTION, and (left, bottom, -near_val)

and (right, top, -near_val) specify the points on the near clipping 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). -far_val speci-

fies the location of the far clipping plane. Both near_val and far_val 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)