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(Typically) Projection Transformations:

One of the following is typically applied in projection mode. This sets the manner in which projection (either perspective or parallel) is performed. In all cases the arguments are of type GLdouble.

glOrtho(left, right, bottom, top, near, far):
Generate an orthogonal projection transformation (projecting along the z axis) where the clipping region consists of points satisfying left <= x <= right, bottom <= y <= top and near <= z <= far. All other points are clipped away.
gluOrtho2D(left, right, bottom, top):
A two dimensional version of glOrtho(), when the z-coordinates are irrelevant. (It sets near = -1 and far = +1.)
glFrustum(left, right, bottom, top, near, far):
Generate a perspective projection transformation and compose it with the current transformation. The parameters specify the bounds of the viewing frustum. The arguments near and far are the distances to the near and far clipping planes along the -z-axis. The other arguments specify the bounds of the viewing rectangle on the near clipping plane.
gluPerspective(fovy, aspect, zNear, zFar):
A more restrictive, but more natural version of glFrustum(). It generates a perspective projection transformation for the given up-down field of view (in degrees), for a window with the given aspect ratio (width/height) and the given near and far clipping planes. It composes this with the current transformation.

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Last updated: Sat, Feb 8, 2003.