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Midasssilver

Reduce Collision Velocity?

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I've seen some posts on the forum regarding this, but I can't seem to get anything working regarding this.

I have an alembic, and I want to be able to extract the intrinsic rotations on the alembic, scale them down, then use that new channel to apply the scaled rotations to the original alembic. This should be able to work with translations as well.

Ultimately, Im trying to reduce the inherited velocity from an alembic, so reducing the movement of the alembic itself is my only option at the moment. I believe what I'm actually seeing is too much collision velocity. The collisions with the smoke is what is causing the look of inherited velocity, and without collisions, it isn't a problem. I believe that's why my workaround was dampening the movement of the alembic so we didn't get as much "collision velocity" for lack of a better term. I've attached a hip file where I'm able to scale the translation of the alembic, sim, then add that translation back. Ultimately what I need to do next, if possible, is scale the rotations as well, so that they remain in the right location/axis. The head turning alembic example I gave you is a good example of how, despite having essentially no translation, we still get the head twisting in each direction, pushing smoke further than I'd like. If I could get a channel for that rotation, scale the rotation down, then re-apply it, I'd be able to limit the "collision velocity" of any alembic I receive. Any help would be appreciated!

 

 

 

 

Import_Alembic_Intrinsics_Problem.zip

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I had a look at the hip file and I can't see the alembic used as a collision object anywhere in the smoke sim.
What I would suggest regardless is looking into the "collision" and "collisionvel" fields that you can source into your pyro sim to have it collide with objects. If you use the "collisionvel" field to source the velocity of the piece that you could just multiply down all the values in the velocity field to scale the collision velocity for all transforms.

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Thanks, Ill give it a shot! Also that abc should have been included in the zip, and if not, I have the setup to write out the alembic in the hip file as well. Will keep u posted about the collision vel

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Here's a hip file where I tested with collisions, without collisions, and with collision vel. Even with my collision vel set to 0, we still get full velocity from the collisions. If I understand collisionvel correctly, it only happens when the fluid contacts the collision geometry. Since my collision geo is inside the source, thats my entire sim. We need collisions in order to have a collision vel, so how can I dampen the amount of velocity we are receiving from collisions?

Collision_Vel_Test_02.hiplc

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9 hours ago, Midasssilver said:

We need collisions in order to have a collision vel, so how can I dampen the amount of velocity we are receiving from collisions?

the static object is internally converting v attribute from your incoming geometry to collisionvel even if you specify a proxy volume to sample collision from. In order for you to scale down your collision velocity you can simply just multiply down your v attribute on your geometry before it is sourced in like so:
image.thumb.png.801173715ec1a7e6fb37b126d1b4441b.png

 

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