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Thread: help about glFrustum

  1. #1
    Guest

    help about glFrustum

    hi,
    I am beginer in OpenGL.
    in work by glFrustum() I have some problems,
    I can`t show my object in viewport,
    i use gluPerspective() and it work good.
    please me if send for me some info about this function and how to work with it.
    i read "redbook" and "OpenGl SuperBible" but not found my answer.

  2. #2
    Super Moderator OpenGL Guru imported_dorbie's Avatar
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    Re: help about glFrustum

    glFrustum is so easy to use that I often wonder why people bother with gluPerspective. Maybe it's just because people like angles.

    The key to understanding glFrustum is simply this.

    You pick your near plane and far plane values, once you've done this, the left right bottom and top values then simply specify a window on the near plane.

    So for a 90 degree horizontal field of view

    if for example you had a near value of 1.0 then left should be -1.0 and right should be 1.0

    If your near plane changed to 5.0 then your left would have to be -5.0 and right would be 5.0 to give you a 90 degree hfov.

    Bottom and top work in exactly the same way.

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