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Thread: glFrustum

  1. #1
    Senior Member Regular Contributor
    Join Date
    Mar 2003


    is the glFrustum command equal to the glOrtho command? I mean in parameters not in perspective(I know that difference).Does the near clipping plane mean first viewable plane on the monitor ? and about gluPerspective - can i specify another x,y,z coordinate interval for screen(not -1,1).everything works fine for me with glOrtho but I want to move in real 3d

  2. #2
    Senior Member Frequent Contributor
    Join Date
    Jan 2003

    Re: glFrustum

    The parameters are the same but with different meaning in a sense. In glOrtho if you want you coords to be 0,0 to 640, 480 great! If you do the same with glFrustum your objects will be placed most likely farther away than you may have thought or the viewing angle will be extreme dependent on the value set for near clip plane.

    A frustum can be thought of as a pyramid with the top cut off at the near clip plane and the bottom as the far clip plane. The values for left, right, bottom, top will be the coords at the near clip plane. Also, if you were to set left right top and bottom notsymmetric about the 0, 0 point, then I believe you get a skewed effect (never messed with it). But, best way to learn is to try it out and see how it goes. gluPerspective is much easier to use and recommended for beginners to get a feel for it.

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