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Thread: Matrix Tranforms

  1. #1
    Member Newbie
    Join Date
    Feb 2002
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    Dallas, TX
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    Matrix Tranforms

    Lets say that there are 1000 objects in a scene, all visible, which are translated by a single modelview matrix, which is NOT the identity.

    Do you get anything at all out of doing the math 1 time, by changing the actual geometry, and replacing the modelview matrix with the identity?

    There are no pushing-popping issues here, since it all uses the same matrix.

    What I really want to know is, do graphics cards handle geometry through an identity faster than through another transform? Are they smart enough to not multiply by 1 and add 0 ?

    Thanks

  2. #2
    Senior Member Regular Contributor
    Join Date
    Apr 2001
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    Greece
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    Re: Matrix Tranforms

    I doubt it(and I hope not).Transforming is a simple process:
    (1) get untansformed vertex
    (2) multiply by transforamtion matrices

    adding something like:
    (2a) if the M=I(which needs 16 compares) don't multiply
    just complicates the whole thing w/o getting you anything.The gain you get in the rare cases where M=I you loose in all the other cases where you need 16 comapres.Plus it messes up the code etc.,etc.

    [This message has been edited by zen (edited 06-24-2002).]

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