glOrtho(3) 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 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)
Typically, the matrix mode is GL_PROJECTION, and (left, bottom,
-zNear) and (right, top, -zNear) specify the points on the near clip-
ping 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_COLOR_MATRIX
glGet with argument GL_MODELVIEW_MATRIX
glGet with argument GL_PROJECTION_MATRIX
glGet with argument GL_TEXTURE_MATRIX
SEE ALSO
glFrustum(3), glMatrixMode(3), glMultMatrix(3), glPushMatrix(3),
glViewport(3)
glOrtho(3)
Mac OS X 10.6 - Generated Thu Sep 17 20:20:26 CDT 2009