Collision Geo changes Bullet Solver behaviour

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I have a rather simple bullet solver SOP setup. A shattered box falls to the ground. As soon as all the constraints of a piece break, said piece starts to shrink.
That all works fine. However, as soon as is introduce a collision geo (a simple box in this case) into the simulation the pieces start to shrink right away while being still "attached" to the constraints.





Quite baffling to me, but probably just some stupid oversight on my part. I would appreciate someone with more experience taking a look at the problem.

I'm using Houdini 18.5.759 for that one.

Cheers!


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Delete your RBD Solver and drop down a new one.
Using Houdini Indie 20.0
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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Unfortunately, that did nothing for me. I got the setup working in Houdini 19 but in 18 I'm still struggling.
I think it has something to do with how I read the Dop Data from the ConstraintGeometry. As soon as there is a Collision Object there might somehow be conflicting data.

Is there a more explicit way to pipe in DOP Data than using $OBJID?
$OBJID/ConstraintGeometry

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Weird, works for me...



Try upgrading to the latest build H19.5.569.

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Using Houdini Indie 20.0
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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If I remember correctly we changed the order in which the collision and rbd objects are created between 18.5 and 19 or 19.5.
In your setup, $OBJID returns the incorrect index and cannot find the constraint geometry, and thus starts shrinking all of the pieces immediately.
Try replacing $OBJID with `dopobjscreatedby("../../rbd_object/")`
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I don't recall if this was added in 19.0 or in 19.5, but the correct approach would be to use the "Use This Object's Data" toggle and just set the data name to "ConstraintGeometry", which will use the ConstraintGeometry subdata of each object the solver is applied to

The $OBJID appraoch doesn't work because this isn't evaluated separately for each object
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