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Thread: Reverse / Time-Remap DMM Simulation Cache?

  1. #1

    Reverse / Time-Remap DMM Simulation Cache?


    Does anyone know of a way to reverse the DMM .xml cache files to play the simulation in reverse, similar to nCache's reverse attribute? (Example, shattering a logo, then reversing it to make the logo look like it's reconstructing from the debris?)

    Also I know there's been a few posts about bullet time and time remapping the simulation, but any efficient tricks for this technique as well? (Subframe caching, editing keyframes in the graph / trax editor, etc etc)

    Any insight would be appreciated, or if this cannot currently be done I would like to request these features!


  2. #2
    This can be done using a workaround.
    cache your DMM sim as normal, then using any substep you would like and alembic cache the results.
    bring in that Alembic cache and set a key frame on the time node for the beginning and the end of the cache. in hypershade, hypergraph or node editor break the connection time has with this newly created "anim" node and break time connections with the Alembic node, now connect your new "anim" time to your Alembic time (same connection "original" time had)
    open your graph editor and swap the end time with the start time in timeline. now your cache will play backwards.
    for proper motion blur in mental ray or vray make sure to expose internal faces before cacheing.
    If you cant figure this out i could make a quick scene for you to see how it works when i get home

  3. #3
    Thanks for the reply mandark,

    I cached the simulation using alembic (although I'm getting a weird issue where the geometry doubles up on itself...). I disconnected the time node from the alembicNode time attribute, then set a key frame on the time attribute with the reverse range and it works! Does that sound right?

    I'll make sure to check expose internal faces for rendering, I'm going to investigate why alembic is messing up the simulation now.

    Thanks so much!

  4. #4
    the reason you are outputting two surfaces is a weird one but simple enough to correct, when exporting to alembic make sure to toggle Renderable only on thatll only process the geo you need rather than the sim tet cage.

    also sounds like if you set your time key frames directly on Time thats essentially a global time change, it may work but its also probably beneficial to have time be "normal" and to correct cache behavior on a per object(s) basis. So if your using a new anim curve to derive your backwards time that is better than using the actual time node in Maya
    Last edited by mandark1011; 09-10-2014 at 07:59 AM.

  5. #5
    Awesome, thanks again mandark.

    As for the time node, I'm not setting a keyframe on the global time1 that maya connects into the alembic cache's time attribute, I'm disconnecting time1 and setting keyframes on the alembic cache's time attribute. I can also make duplicates of the alembicnode, connect that into multiple duplicates, and make unique re-timing for the multiple duplicates using the same cache under this keyframing method. Or maybe I'm not understanding correctly?

    Also also, is the only way to keep material/shader information in an alembic cache by using the import/merge function? Seems to work fine for me, but just curious

    I've been testing with Maya 2015 for reference.

  6. #6
    glad to hear its working for you. I'd say if its working the way youd like and you can plug and play like that the technique is working fine.

    I think the Import/merge function is the preferred method, to be honest most of my tests are on grey scale geometry as im exploring sim based RnD only right now versus actual renderable geo.

    I am using 2015 as well and it seems that with the alembic integration and the tool chain fixes DMM is super stable in this release.

    Might be worth mentioning that in the Alembic Exporter for Maya 2015 it is no longer necessary to expose internal faces, you can export Vector Colour Sets with your alembic export now that will allow mental ray and Vray to render motion blur on geometry with changing point order.

    good luck


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