I've imported an Alembic character sequence from Softimage (with point velocities exported) and created a shirt cloth object.
Collision does not work and I presume it is because it is a sequence of meshes with no velocity data on them? Not sure why Houdini can't see/read the exported point velocities.
What would be the right way to get this to work?
Cloth collision with Alembic mesh not working.
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- Werner Ziemerink
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- mandrake0
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1. you can check the collition mesh if its correct:
dop network => collision geometry (RBD Object node) => Collitions (tab: RBD Solver) => Collition Guide (tab: volume)
make the viewport to wireframe
2. add the ability to generate on each frame:
dop network => collision geometry (RBD Object node) => Use Deforming Geometry
i think one of these two are the cause of the problem but not 100% sure.
some tutorials:
https://www.sidefx.com/index.php?option=com_content&task=view&id=2622&Itemid=344 [sidefx.com]
https://www.sidefx.com/index.php?option=com_content&task=view&id=2350&Itemid=344 [sidefx.com]
dop network => collision geometry (RBD Object node) => Collitions (tab: RBD Solver) => Collition Guide (tab: volume)
make the viewport to wireframe
2. add the ability to generate on each frame:
dop network => collision geometry (RBD Object node) => Use Deforming Geometry
i think one of these two are the cause of the problem but not 100% sure.
some tutorials:
https://www.sidefx.com/index.php?option=com_content&task=view&id=2622&Itemid=344 [sidefx.com]
https://www.sidefx.com/index.php?option=com_content&task=view&id=2350&Itemid=344 [sidefx.com]
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- Werner Ziemerink
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Nevermind. I found a workaround.
If anyone is interested…
- Export just first frame of your character mesh as obj or alembic.
- Use this static mesh as the collider and append a point SOP after the file node.
- Use the alembic sequence as the second input of the point SOP and set the expression to $TX2 $TY2 and $TZ2
Done!
Thanks mandrake. I will have a look and let you know if it works.
If anyone is interested…
- Export just first frame of your character mesh as obj or alembic.
- Use this static mesh as the collider and append a point SOP after the file node.
- Use the alembic sequence as the second input of the point SOP and set the expression to $TX2 $TY2 and $TZ2
Done!
Thanks mandrake. I will have a look and let you know if it works.
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- VFX_Skull
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- tiansicong44
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- Midasssilver
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- anbt
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Werner Ziemerink
Nevermind. I found a workaround.
If anyone is interested...
- Export just first frame of your character mesh as obj or alembic.
- Use this static mesh as the collider and append a point SOP after the file node.
- Use the alembic sequence as the second input of the point SOP and set the expression to $TX2 $TY2 and $TZ2
Done!
Thanks mandrake. I will have a look and let you know if it works.
Hello, I am quite late to the party but I have I think a similar issue.
I drapped some kind of dress around a Mixamo model. It works fine but then, when I start my sim and my model starts walking, the dress doesn't collide at all. I realised it was because I edited the model and the topology is changing every frame. I mean the points of the model are changing each frame. The mesh isn't really static. I guess it happened because I inflated some body parts with VDBs and now the arms are merging with the hips as the model is walking, but I want to keep that effect.
So I thought that was the cause of my collisions problems. I tried with a normal Mixamo sequence and I didn't have any issues. So It definitely is because of the changing topology of my model.
It seems that the solution would be to convert my walking model into a collision VDB object (correct me if I am wrong) and do this in DOPS, import the drape as vellum source. But it still doesn't work
My static object in DOPS (my walking model) is set to:
- use deforming geometry
- create active object (tried both on and off)
- collisions detection set to volume (I also tried surface)
- Volume sample mode
It is not working. The cloth is kind of colliding, but intersect with my model and it is really jittery.
I have increased substeps with no change.
Any clues?? I tried what you said with the Point SOP, but my mesh doesn't move after putting this expression in it.
Thanks a lot
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- jsmack
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I'm not sure vellum works with volume collisions. It has its own way of computing collisions based on the mesh since it's pbd.
Use an animation that doesn't have changing topology. It's very abnormal for skeletal animation to wind up with changing topology. I would retrace my steps to try to resolve that problem before doing anything. Changing topology makes it impossible to compute velocities or motion blur.
Use an animation that doesn't have changing topology. It's very abnormal for skeletal animation to wind up with changing topology. I would retrace my steps to try to resolve that problem before doing anything. Changing topology makes it impossible to compute velocities or motion blur.
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- anbt
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jsmack
I'm not sure vellum works with volume collisions. It has its own way of computing collisions based on the mesh since it's pbd.
Use an animation that doesn't have changing topology. It's very abnormal for skeletal animation to wind up with changing topology. I would retrace my steps to try to resolve that problem before doing anything. Changing topology makes it impossible to compute velocities or motion blur.
Thanks for your answer. Ok, so the problem comes from Vellum then.
What would be the process to make a cloth collide with a deforming VDB? I tried with a mesh that doesn't have a changing topology and it works fine but I would like to find a solution for something that is changing topology.
Edited by anbt - 2021年1月21日 14:59:49
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- jsmack
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- anbt
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- mrCatfish
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Have you also looked at this thread? https://www.sidefx.com/forum/topic/77472/ [www.sidefx.com]
Sean Lewkiw
CG Supervisor
Machine FX - Cinesite MTL
CG Supervisor
Machine FX - Cinesite MTL
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- anbt
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mrCatfishyes this is also me in this thread
Have you also looked at this thread? https://www.sidefx.com/forum/topic/77472/ [www.sidefx.com]
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