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[SOLVED] 3ds Max 2025: FBX Export with Path deform for Unity

ColMatrix
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ColMatrix polycounter lvl 3
Hello,

I have animated a vertical shutter with slats using a Path Deform modifier. Upon exporting to FBX the keyframes are lost. As seen in other threads, people found a solution by using collapseTo, to 'bake' the keyframes. Unfortunately, this doesnt work for me or Autodesk apparently. After contacting Autodesk Product Support and several tests including 3rd party plugins, the only available option (at this time) was to use the file format .abc (Alembic) which seems to work - great!

But, what if the project developers refuse to accept this file type (maybe there are other issues with Alemic and the project asset requirements). Is my only option then to painfully Keyframe the shutter?

All pearls of wisdom are welcome! Thanks!

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  • Noren
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    Noren greentooth
    The path deform modifier deforms the mesh, so you'll have to export it in form of a vertex animation / point cache, which is why you need Alembic. You could try a Morpher perhaps if the transition between open and closed is linear (but then you probably wouldn't need a path deform).

    If you want a collapsable animation (which would likely mean a bone or object for each shutter panel), then the path constraint animation controller is the right choice.


    Edit: Seems like FBX can export/reference point caches after all. Haven't tried it, though, and no idea if Unity imports it.
    https://download.autodesk.com/us/fbx/2013/3ds_Max_FBX_Plug-in_Help/index.html?url=files/GUID-691D1194-AE6E-4EE9-A6A3-F1797D2F3B27.htm,topicNumber=d30e2947

    Very broadly speaking, bone animation is usually the preferred method for realtime graphics, but if your shutter is very lowpoly, it might make no real difference.
  • ColMatrix
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    ColMatrix polycounter lvl 3
    @Noren

    Many thanks for your response. After exporting an FBX file with a Cache file and re-importing in 3ds Max the kayframes were there! Many thanks, now the Unity developers are looking into it, if we can use it within our Unity project. 

    Thanks for taking the time, to post your suggestion!
  • ColMatrix
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    ColMatrix polycounter lvl 3
    @Noren Unfortunately Cache files will not be imported into Unity, without a 3rd party tool. 

    I have found a post on Autodesks Forums with a max file using bones as you suggested, which seems to work pretty well. I hope I can use it as reference.

    https://forums.autodesk.com/t5/3ds-max-animation-and-rigging/problems-animating-along-spline-path/td-p/7427833




  • Noren
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    Noren greentooth
    Just tried it, and the Spline IK is a very good addition. 
    Note that the important part in step 5 is to replace the XYZ position sub-controller with a path contraint (or use a list controller like seen in the image). He probably started to write that, but then jumped ahead to the bezier float. Or maybe that used to be the default setup of the controllers for the Spline IK back then.
  • ColMatrix
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    ColMatrix polycounter lvl 3
    @Noren

    Thanks for the confirmation - If I understand you correctly - should it look something like this?:



    On another note, i am also seeing something, that I did not intend for and I have been unsuccessful in figuring it out. The 'Motion Paths' show, that the IK Chain (Green), and Bone (White) Paths do not follow exactly the chosen Spline Path (purple). No one would probably see this detail - but it annoys the hell out of me and for future projects maybe this issue is noticeable...any ideas whats causing this? Thanks once again.

  • Noren
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    Noren greentooth
    The controllers look good to me.

    As for the motion paths, how fast is your shutter unrolling? If each straight line is the motion from one frame to the other, then a slower animation would give you more "segments".  
    As for the points not lying exactly on the spline, that might just be due to geometry. Your bones are straight and can't stretch (both points move at the same speed) so they can't follow each and every curvature perfectly. At least that would be my guess. The distance to the IK goal can shrink, but only by bending the overall chain, which would result in some bones moving away from the spline.
    But maybe you could try putting a Normalize Spline modifier on your path and see if that helps.
  • ColMatrix
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    ColMatrix polycounter lvl 3
    @Noren Normalize Spline did the trick! Thank you very much for your help
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