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Thread: Instances and Motion Buffers: Broken?

  1. #1
    Super Member dwburman's Avatar
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    Instances and Motion Buffers: Broken?

    Hi, I'm trying to figure out a post-effect motion blur workflow, but it looks like the motion buffers are seriously screwed up when using instances. Is there a trick to get it to work?

    Here's the Y motion buffer without the instances turned on:
    Click image for larger version. 

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    Here's the Y motion buffer with instances turned on:
    Click image for larger version. 

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    Here's an experiment using DP filter to combine the Y and X buffers into something Reel Smart Motion Blur can use:
    Click image for larger version. 

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    Incidentally, if I just use LW's built-in Vector Blur image filter, the blur is all wrong too and looks like a zoom blur originating in the lower right quadrant of the image.

    Is there a way to fix or work around this?

    MotionVectorsAndInstances.zip

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  2. #2
    Super Member dwburman's Avatar
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    Is this a known issue? Can someone confirm it?
    [mr] Dana W. Burman | http://dwburman.com
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  3. #3
    skeptic lertola2's Avatar
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    There was one point a year ago when I tried to get something out of lightwave that would work with Reel Smart Motion Blur. Despite a lot of advice from very smart people on this list I was never able to get it to work properly. Even non instanced geometry has the same problem I think. I would love to have someone in the know post a clear explanation of how to get to get motion vectors out of lightwave and into aftereffects with RSMB. It is still a mystery to me.

  4. #4
    Super Member dwburman's Avatar
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    I got an email back about my bug report and the problem didn't happen on the latest build, so I hope 11.5 is ready before I need to render.

    Here's a video showing my experimental setup for a LW to RSMB Workflow:

    [mr] Dana W. Burman | http://dwburman.com
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  5. #5
    Super Member dwburman's Avatar
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    double post
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  6. #6
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    Hi,

    Just checking to see if anyone know if this problem has been fixed.

    Thanks

  7. #7
    Super Member dwburman's Avatar
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    I've been told (on my bug report ticket) that this issue wasn't occurring in newer internal builds, so it should be fixed for LW11.5.
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  8. #8
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    I am still having problems with 11.03.

    I suppose we just have to wait for 11.5...

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    I have tested in LW 11.5 and there seems to be no difference.

    Can anyone confirm that motion x and motion y buffer still does not work correctly for instances? Does anyone knows any work around?

    LW 11.5 is awesome all around but I really need to figure out this problem (or if there actually is a problem). Really appreciate any feedback.

    Thanks in advance.

  10. #10
    Hey, what's goin on... this is unnerving issue for a long time... Isn't this fixed in LW11.5??

  11. #11
    Red Mage Celshader's Avatar
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    Lightbulb

    Quote Originally Posted by VermilionCat View Post
    Hey, what's goin on... this is unnerving issue for a long time... Isn't this fixed in LW11.5??
    Random thoughts:

    • LightWave 11 instances never delivered the correct motion vector information.
    • As far as I know, 11.5 does not fix it.
    • Our compositing pipeline for LW11 Instances at work is no different than the one we used for the volumetric-based DP_Instance, which can show up in almost every render buffer except for Motion Vectors.


    More random thoughts:

    • FiberFX motion vectors were added in 10.1, but lost in 11.0.x.
    • FiberFX motion vectors were restored in 11.5. So that motion vector issue has been fixed.
    Last edited by Celshader; 02-02-2013 at 11:37 AM.
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  12. #12
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    Hi celshader,

    Thanks for your thoughts. Can you elaborate how you deal with instances in compositing if it cannot use motion vectors. Does this means that you have to fo the motion blur during render? Practically all my scenes have instances...

  13. #13
    Almost newbie Cageman's Avatar
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    Quote Originally Posted by sukardi View Post
    Hi celshader,

    Thanks for your thoughts. Can you elaborate how you deal with instances in compositing if it cannot use motion vectors. Does this means that you have to fo the motion blur during render? Practically all my scenes have instances...
    For things lying flat on the ground, you can create a new scenefile that only renders motionvectors, that does not contain any instances at all. We have some shots where there are tons of small things lying on the ground, and doing it this way works fine!

    For larger things, such as trees etc, the only way to get something that kind of works, is to, again, create a new scenefile and place spheres or boxes where the instances are and render thouse with MVectors. In comp, you then use the alpha from the instances as a mask and "project" the motionvectors onto the instances. This doesn't give you exact MBlur, but close enough to make it work.

    This technique was used a couple of times for smoke-effects we did in Max in order to get motionvectors for it.
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  14. #14
    Red Mage Celshader's Avatar
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    Quote Originally Posted by sukardi View Post
    Hi celshader,

    Thanks for your thoughts. Can you elaborate how you deal with instances in compositing if it cannot use motion vectors. Does this means that you have to fo the motion blur during render?
    Yes, for those elements that use instances. For example, on a creature show using LightWave 10.1 we had a creature kicking up instanced straw (DP_Instance). The creature was rendered without motion blur, and motion vectors handled the creature's motion blur in comp. The instanced straw was rendered with in-camera motion blur and mixed into the comp.

    Mixing real and post-process motion blur should get a bit easier with LightWave 11.5, since 11.5 offers the ability to render centered motion blur with its "Shutter Open" offset option in the Camera panel. Nuke's Vector Blur could be shifted, but Reel Smart Motion Blur in After Effects was always centered no matter what. Now LightWave's in-camera motion blur can be centered, too.
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    Thanks a lot Cageman, Celshader.

    You guys really knows your stuff...

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