# FreeBSD Manual Pages

```GLORTHO()							     GLORTHO()

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 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 {"zFar" - "zNear"}}  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 ~=~ -{{"zFar" + "zNear"} over {"zFar" - "zNear"}}

Typically,  the	matrix mode is GL_PROJECTION, and (left, bottom,  -zN-
ear) and	(right,	top,  -zNear) 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).
-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_MODELVIEW_MATRIX
glGet with argument GL_PROJECTION_MATRIX
glGet with argument GL_TEXTURE_MATRIX

SEE ALSO
glFrustum, glMatrixMode,	glMultMatrix, glPushMatrix, glViewport

GLORTHO()
```

NAME | C SPECIFICATION | PARAMETERS | DESCRIPTION | ERRORS | ASSOCIATED GETS | SEE ALSO

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