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glOrtho
Chapter 13
314
glOrtho
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 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:
A 0 0 t
x
0B0t
y
0 0Ct
z
0001
where
A = 2 / (right left)
B = 2 / (top bottom)
C = 2 / (far near)
t
x
= (right + left) / (right left)
t
y
= (top + bottom) / (top bottom)
t
z
= (zFar + zNear) / (zFar zNear)
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