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Thread: Projection and Modelview matrices

  1. #1
    Guest

    Projection and Modelview matrices

    Hello

    I wonder what do I get from multiplying
    projection and modelview matrix. I get
    a pack o 16 numbers but what do they mean?
    I know I can get many information about
    for example frustrum but how?

    Thanks

  2. #2
    Senior Member Regular Contributor
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    Westerville, Oh, USA
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    Re: Projection and Modelview matrices

    I found this description by googling on comp.graphics.api.opengl:

    OpenGL has the following (and I assume you are interested in OpenGL, since
    this is the OpenGL newsgroup)...

    Object coordinates
    multiply by ModelView matrix to get...
    Eye Coordinates
    multiply by Projection matrix to get...
    Clip Coordinates
    multiply by 1/W to get...
    Normalized Device Coordinates
    scale/translate according to the specified viewport to get...
    Device Coordinates


    [This message has been edited by starman (edited 07-09-2003).]

  3. #3
    Guest

    Re: Projection and Modelview matrices

    Originally posted by starman:
    I found this description by googling on comp.graphics.api.opengl:

    OpenGL has the following (and I assume you are interested in OpenGL, since
    this is the OpenGL newsgroup)...

    Object coordinates
    multiply by ModelView matrix to get...
    Eye Coordinates
    multiply by Projection matrix to get...
    Clip Coordinates
    multiply by 1/W to get...
    Normalized Device Coordinates
    scale/translate according to the specified viewport to get...
    Device Coordinates


    [This message has been edited by starman (edited 07-09-2003).]
    Woow. Thanks.

    Really I was interested how to use it for frustrum culling. Multiplying modelview matrix by projection matix gives ... something. And on www.gametutorials.com the use this 'something' to cull objects.
    What do you think about that?

    Thanx

  4. #4
    Senior Member Regular Contributor
    Join Date
    Feb 2003
    Location
    Westerville, Oh, USA
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    Re: Projection and Modelview matrices

    The application I'm working on is pretty small scale...only a handful of objects. I haven't had the need to do frustum culling yet. However, I did research it months back as was pointed to this article. I think you might find it helpful:
    http://www.markmorley.com/opengl/frustumculling.html

    [This message has been edited by starman (edited 07-10-2003).]

  5. #5
    Guest

    Re: Projection and Modelview matrices

    Thanks!

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