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Nick da Silva

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  1. I've attached a very simple scene demonstrating the problem. I really hope someone can help with this. Thanks. constraints4.hip
  2. Hi all I'm trying to constrain active objects in DOPs to deforming geo. The problem is that since the constraint network is only being created on frame 1 then inside of DOPs the constraints don't update with the deforming geometry. I can't import the constraint network every frame either because then the constraints are recreated every frame even if they were deleted the previous frame. Does anyone have a good workflow for this or suggestions? Thanks!
  3. Your bounding box is not set correctly. Your constraints are still holding the active pieces to the inactive pieces. I made a small change to your SOP solver in DOPs and it works now. DOP_SIM.hipnc
  4. What does your collision geometry look like? Can you attach the hip file?
  5. In my experience this is usually a grid scale issue. Grid scale of 0.5 seems very low (I think the default is 2). Try reducing it from 2 in smaller increments. Perhaps start at 1.9 or 1.8 and test from there.
  6. Thanks David. Using the hou.frame() python expression I was able to write out the sub frames as well and it works great! Really appreciate your help!
  7. Ok, so I publically confess my stupidity. Thanks David and John for taking the time to help me I was writing out my geo after modifying the topology but before converting it to VDB for collision. So I was being forced to use the timeblend to try to create the sub frames for me which is what was not working. So if I go back and remove the writing out of the geo and let it calculate the vdb all the way from the original geometry (which has consistent topology so the sub frames interpolate correctly). It's a silly mistake but I was trying to speed things up by writing out the data. Anyway, it seems to be working now. Hopefully this can help someone else from making the same mistake. John. Thanks for the reply. I'll definitely look into that as another solution if I run into more problems.
  8. Thanks so much! That's interesting. I've been using the collision source node to create my collision geo. Yours seems to work just fine with the primitive count changing even on sub frames.
  9. Hi David Yes, I've done plenty of tests and none of them work. The sub frame interpolation freaks out because the point order is completely different from frame to frame. Then when it gets to the next integer frame it jumps back to the correct collision geo and there is plenty of penetration and the particles go crazy.
  10. Hi all! I'm trying to do a PBD sim of a character who's body turns into sand over time. My problem is that I'd like the sand as it falls to collide with the moving body but obviously the parts of his body that have turned into sand should no longer be collided with as they are no longer there. This poses a big problem that I have not found a solution for. How do you have a collision object that's topology is changing over time? Houdini cannot interpolate between frames where the point count/order changes which makes complete sense but what is the alternative? Can anyone offer a solution or alternative approach for me? In the attached file you can see the spread (in red) where the character is turning into sand. The parts that are not red need to remain as collisions. Thanks so much!
  11. I wanted to but the project is large with many referenced files. Is there a good way for me to share this?
  12. Hi all. I hope someone can help me with this. I have a previously simmed out geo (alembic) inside my dopnet as a static deforming object and I'm trying to sim a simple rigid body collision with an RBD object. I'm getting a strange result where no matter what my settings are there seems to be no friction between the two objects. I have attached two screenshots, one showing the collision geo and one showing the actual geo. Any ideas? Thanks!
  13. Hi Edward Thanks for the reply! That's exactly what I needed to know.
  14. I'm trying to familiarize myself with the FEM solver in Houdini with a very simple scene however I keep getting a warning on my Solid Object in side DOPs. The solid object itself does not error out when initialized however when I enable to FEM solver then the warning appears. The warning is: created group "fe_quality_bad" with 71 bad primitives Anyone know what might be causing this? FYI, it's not breaking the sim but I just want to know for my own understanding. Thanks!
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