Thread: Triangulating a plane

  1. #1
    The Right Honourable psychopath's Avatar
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    Triangulating a plane

    Was looking at the CSX format used by Torque Constructor, to see if I might be able to write a loader for it. Luckily it's XML, so no probs there.

    But one thing that's throwing me off, is the way faces are defined in the file:
    <Face id="36" plane="1 -0 0 -2" material="uvchart128" texgens="-0 0.25 0 0.5 0 0 -0.25 -0.5" texScale="1 1" texDiv="128 128" />
    How does one go about making triangles out of a plane as defined here?
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  2. #2
    Registered User VirtualAce's Avatar
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    I'm sort of confused as to what you mean since any 3 points in space, thus any triangle, form a plane.

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    Software Developer jverkoey's Avatar
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    Are there vertices elsewhere in the file that link to that face id? Seems kinda silly that they'd have a separate vertex and face tag, but who knows.

  4. #4
    The Right Honourable psychopath's Avatar
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    Quote Originally Posted by jverkoey
    Are there vertices elsewhere in the file that link to that face id?
    Nope, that's the problem.

    Usually in a file containing geometry info, I get lists of faces, vertices, and indices. In this file, all I get is face info with that plane definition.

    Quote Originally Posted by Bubba
    I'm sort of confused as to what you mean since any 3 points in space, thus any triangle, form a plane.
    What I mean is, basically, that I have no idea what the values given for the plane mean/do, and how I would take that information, and create a triangle out of it.

    EDIT: ugh, well now I'm confused. I just tried a different CSX, and I get the vertex info and stuff. I thought it might have been because the first one I tried was just some boxes, but I tried saving another with just a cube, and I get vertices for that too. Weird.

    I'm still curious about what to do if I just have a plane, though .
    Last edited by psychopath; 07-12-2007 at 10:01 AM.
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    A guess is that the plane might be defined as the normal + a scalar D.

    For all the points (P) on the plane, something like the following is true: D = -dot(P, normal).

    Not easy to do anything else if you should represent an infinite plane.

  6. #6
    Registered User VirtualAce's Avatar
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    The only thing I can think of is perhaps they are representing a plane by:

    ax+by+cz+dw=0

    That would explain the four numbers.

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