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Thread: Tension Based Displacement

  1. #1
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    Tension Based Displacement

    Anybody had any luck getting a mesh to displace in areas of stress/compression (ie for wrinkles and such) on a UV mapped object? The DP Tension node works for bumps, but I'm finding it's adding mysterious blocky artifacts when used for displacement. Stress maps also do bumps, but seem to disregard normal vectors when used for displacement.

    Thanx.

    (c:
    Last edited by Chris Jones; 11-07-2012 at 04:04 AM.

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    Quote Originally Posted by Chris Jones View Post
    Anybody had any luck getting a mesh to displace in areas of stress/compression (ie for wrinkles and such) on a UV mapped object? The DP Tension node works for bumps, but I'm finding it's adding mysterious blocky artifacts when used for displacement. Stress maps also do bumps, but seem to disregard normal vectors when used for displacement.

    Thanx.

    (c:
    Tension node is not a shader, so I don't think that it adds artefacts by itself,
    since it just analyses the geometry, it is important to detail your entire scene setup
    for understanding this issue.

    Denis.

  3. #3
    Goes bump in the night RebelHill's Avatar
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    Quote Originally Posted by Chris Jones View Post
    seem to disregard normal vectors when used for displacement.
    How are u going about using it... ideally your displacement map is what ought be regarding the normal (direction), stress node output should simply be used to add/multiply the scalar component (length).
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    Quote Originally Posted by dpont View Post
    Tension node is not a shader, so I don't think that it adds artefacts by itself,
    since it just analyses the geometry, it is important to detail your entire scene setup
    for understanding this issue.

    Denis.
    Hi Denis - is this to say the tension node can do displacement under normal circumstances? If so I'll poke around some more and try to pinpoint the problem before I go into details.

    Quote Originally Posted by RebelHill View Post
    How are u going about using it... ideally your displacement map is what ought be regarding the normal (direction), stress node output should simply be used to add/multiply the scalar component (length).
    I've tried so many different things I don't rightly remember...! At this point I mainly wanted to check whether I'm barking up the wrong tree by trying to use Tension or StressMap for this - if they're known to work with displacements though I'll have another crack at it and let you know what I did exactly.

    Thanks guys,

    (c:

  5. #5
    Goes bump in the night RebelHill's Avatar
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    here... scale the bone to see the effect. This is done both way, by default, in the surface ed, using bump displace. Done this way it just uses the geo/subD normal by default and animates fine, but is non interactive. Toggle bump off and disp nodes on, and u have the vector defined method, and it is interactive.
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    Thanks for the examples - I had mine wired differently, but am getting the same effect. If you put another bone in there and ramp up the SubPatch level you can see what I'm on about. It's more evident when Subdiv order is set to After Motion (which is where I need it to be). It's not cooperating with subdiv surfaces by the looks of it...

    tension2.lws

    (c:

  7. #7
    Goes bump in the night RebelHill's Avatar
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    No good... subdivision has to be before displacement... ie after bones, to use these effects. Thats your problem, and there's no way round it.
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    It happens whatever the subdiv order. I've also just found that it doesn't even have to be subdivs - if you freeze the object, the problem is still there. Seems that it doesn't like 3-way poles..?

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    Quote Originally Posted by Chris Jones View Post
    It happens whatever the subdiv order. I've also just found that it doesn't even have to be subdivs - if you freeze the object, the problem is still there. Seems that it doesn't like 3-way poles..?
    This more a limitation caused by the high Subd level,
    so a frozen model is obviously better to use,
    or no good result over 9/10 Levels,
    in both surfacing or displacement context.

    Denis.

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    Hmm... are you sure? I can still see blocky ridges at very low SubD levels, just not as defined obviously. And it's still there in a frozen model, but not as pronounced. Also, it looks like it's not restricted to 3-way poles after all; if you freeze the object in the example and subpatch it again, you get zig-zagging ridges in my 2-bone version of the scene, as if half of the polys have been smooth shifted. It's quite evident even at a SubD level of 3.

    None of this occurs when textures are applied directly as a displacement though.

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    Quote Originally Posted by Chris Jones View Post
    ...None of this occurs when textures are applied directly as a displacement though.
    Again, it is not texture mapping neither a shader,
    (despite its weird location in DPKit folder)
    each time you add or remove geometry, tension node
    gets different results, accumulating edge measurements
    giving a local bilateral tension, the actual formula
    is indeed not smooth with a high subdivided model.
    Tension doesn't measure displacement distance
    but averages all edge tensions around a point.

    Tension node may reveal appropriate stressed area
    for mapping on a well balanced model, not in this case.

    Denis.

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    Not sure I fully understand, but I shall take your word for it.

    What would constitute a well balanced model?

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    Quote Originally Posted by Chris Jones View Post
    Not sure I fully understand, but I shall take your word for it.

    What would constitute a well balanced model?
    You have no power about the 'balancement' of the
    subdivision for such shape in Lightwave, I mean
    the order of subpatches for adjacent cage polygons
    and the order of vertices when LW is creating sub-polygons,
    the limitation is intrinsect to the node when it is going to average
    edge tension,
    you just expect too much from this simple,
    and fast algorithm.

    Curvature node is more complex but for averaging surrounding
    edge angles and slower, I'm not not sure that it could be usefull for
    displacement.

    Denis.

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    Ok, sounds like I'm not going to win the battle with Tension then... thanks for the clarification Denis. I don't think I can get what I'm after with Curvature, but that looks like it might come in handy for other things...

    So... anybody know of any other ways to selectively affect displacements? Any reports of success with StressMaps?

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    Quote Originally Posted by Chris Jones View Post
    So... anybody know of any other ways to selectively affect displacements? Any reports of success with StressMaps?
    With an 'area' mode instead of edge,
    result is far better..

    Click image for larger version. 

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    Denis.

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