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model overlap at certan distance - Macromedia Director 3D

Hi, Here is my problem: I have a scene with models, cameras, textures, etc. When I export this scene i see strange things like models that overlaps at certain distance from the camera. I whould like to know if anyone of you had that problem before an who you resolved it. Many thanks in advance....

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  1. #1

    Default model overlap at certan distance

    Hi,

    Here is my problem:

    I have a scene with models, cameras, textures, etc. When I export this scene i
    see strange things like models that overlaps at certain distance from the
    camera. I whould like to know if anyone of you had that problem before an who
    you resolved it.

    Many thanks in advance.

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    ensamblador Guest

  2. #2

    Default Re: model overlap at certan distance

    Hi,

    Yes, i think I had such a problem, Try setting the camera(from witch you are viewing) hither to a greater value.
    --
    w3d.camera(1).hither = 50
    --
    That solved my problem.

    Daniel.
    danieloizo Guest

  3. #3

    Default Re: model overlap at certan distance

    And if that doesn't work, try scaling the camera by a large factor like
    10-20 or so.

    sprite(the currentSpriteNum).camera.scale = vector(20,20,20)

    If you build the scale of the world too small it can suffer from the
    Z-buffer sorting issue, especially on older cards, and enlarging the
    camera's viewing frustum can compensate for it.

    Cheers

    Richard Smith


    Richard Guest

  4. #4

    Default Re: model overlap at certan distance

    Oops, sorry that should have read...

    sprite(the currentSpriteNum).camera.transform.scale = vector(20,20,20)

    Richard Smith


    Richard Guest

  5. #5

    Default Re: model overlap at certan distance

    Thanks for the quick replies. I remember that problem too danieloizo, and i
    solved scaling the camera and/or playing around with hither yon values.

    In this case tweaking the camera makes no diference, i've tried. By unkowledge
    i didn't mention the part that the models with problems have transparency.
    Fontunately i have found this thread on director-online that describes the
    cause of the problem(two transparent models, see the shckwave movie whitin).

    Maybe there is a way to correct this z-buffer problem, or maybe not. I leave
    this thread open.


    ensamblador Guest

  6. #6

    Default Re: model overlap at certan distance

    The problem is that models which have transparent textures are sorted
    per-model, by their geometric centre. Here's a detailed description of when and
    why the problem occurs:
    http://nuttybar.drama.uga.edu/pipermail/dir3d-l/2005-February/008031.html

    The solution is to break the model down into separate parts, so that each part
    is sorted by its own geometric centre.

    As a demo - here are 2 cubes, each sitting on opposite sides of a long wall:

    http://www.robotduck.com/models/?x=-240&y=35.00&z=40.00&t=79&a=-270&d=728.2&dir=
    alphaSort&file=alphaCubesAlphaWall

    Both the cubes and the wall have alpha textures with transparency. As the view
    rotates, each object is sorted only by its distance from the camera, causing
    the cubes to appear to 'pop' in front of and behind the wall as their geometric
    centre becomes closer/further to the camera than the wall's geometric centre.

    In this fixed scene, the wall has been split into 3 separate models, thereby
    causing each separate piece to be sorted independantly by its geometric centre.
    This reduces the chance that a cube's centre will be closer to the camera than
    a wall which is supposed to occlude it.


    http://www.robotduck.com/models/?x=-240&y=35.00&z=40.00&t=79&a=-270&d=728.2&dir=
    alphaSort&file=alphaCubesAlphaWallSeparated

    If you watch carefully however, there are still moments where the sorting is
    incorrect and they overlap. This could be fixed by breaking up the wall into
    still smaller sections.

    Increasing the 'hither' value of the camera is not the correct solution in
    this case. It is the correct solution to a different problem with overlapping
    models however, called 'z-fighting' : http://en.wikipedia.org/wiki/Z-fighting

    hope this helps!

    - Ben


    duckets Guest

  7. #7

    Default Re: model overlap at certan distance

    Hi,

    Very well explained duckets , It's good to know about this z-buffer problem.

    Daniel
    danieloizo Guest

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