glOrtho(3G) OpenGL Reference 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 near,
GLdouble far )
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, far 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 t |
right-left x
| |
| _____2____ |
0 0 t
| top-bottom y |
| |
___-2___
| 0 0 t |
far-near z
| |
| 0 0 0 1 |
| |
where
right+left
t = -
x right-left
top+bottom
t = -
y top-bottom
far+near
t = -
z far-near
Typically, the matrix mode is GLPROJECTION, and (left, bottom, -near)
and (right, top, -near) 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
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glOrtho(3G) OpenGL Reference glOrtho(3G)
specifies the location of the far clipping plane. Both near and far can
be either positive or negative.
Use glPushMatrix and glPopMatrix to save and restore the current matrix
stack.
ERRORS
GLINVALIDOPERATION is generated if glOrtho is executed between the
execution of glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGet with argument GLMATRIXMODE
glGet with argument GLMODELVIEWMATRIX
glGet with argument GLPROJECTIONMATRIX
glGet with argument GLTEXTUREMATRIX
SEE ALSO
glFrustum, glMatrixMode, glMultMatrix, glPushMatrix, glViewport
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