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 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:
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 specifies 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
