OK, I have a truly bizarre one for you.
If you put enough Obi Colliders overlapping in the same place, even fully static box colliders, the Compute backend goes absolutely mental. It has some kind of overflow and starts adding random updraughts of force to particles in random areas, some near the colliders (but not touching) and some nowhere near it. Burst is unaffected.
I noticed it in a game where I have a level made out of modular parts and each Wall has an obi collider. I added some more colliders to the level and noticed that my fluid started randomly jumping up all over place and wouldn't stop. Even with the most aggressive smoothing, the fluid never reached a rest state and just kept jiggling. A ton of trial and error to find out that it's caused by obi colliders just being in the scene and switched on and not even necessarily near the fluid, and then I managed to recreate it by stacking enough colliders in the same spot.
Replication steps:
Observed Result: Fluid going mental
If you put enough Obi Colliders overlapping in the same place, even fully static box colliders, the Compute backend goes absolutely mental. It has some kind of overflow and starts adding random updraughts of force to particles in random areas, some near the colliders (but not touching) and some nowhere near it. Burst is unaffected.
I noticed it in a game where I have a level made out of modular parts and each Wall has an obi collider. I added some more colliders to the level and noticed that my fluid started randomly jumping up all over place and wouldn't stop. Even with the most aggressive smoothing, the fluid never reached a rest state and just kept jiggling. A ton of trial and error to find out that it's caused by obi colliders just being in the scene and switched on and not even necessarily near the fluid, and then I managed to recreate it by stacking enough colliders in the same spot.
Replication steps:
- Create a new blank URP project
- Install Obi Fluid 7.03
- Launch Faucet And Bucket test scene and fix the scene materials
- Set the Solver to Compute back-end and the emitter to speed 6 and lifespan 8
- Edit the fluid blueprint to expand it to 12,000 particles and re-generate it
- Create a 3D Cube at coordinates Vector3(0.879999876,1.23000002,-2.41999984). Add an Obi Collider.
- Launch the Scene. Now duplicate the cube in place using Ctrl-D until you get to 16 cubes.
- When you get to 16 cubes, you'll see obvious jets shooting out of the fluid below and near the cube, and another jet randomly on the far edge of the fluid.
- If you disable the obi colliders on the cubes 1 at a time you can see the effect diminish with each one.
- If you move any of the cubes so that their colliders are no longer overlapping, they no longer contribute to the effect.
- If you move the group of cubes around or re-scale them all, it changes the characteristics of the random bits of force causing the jets
- Change the box collider size's y value on all the cubes slowly. When it hits 3, an entire quadrant of particles randomly jumps up in the air. Increase it further to just over 8.0, the effect disappears and everything goes back to normal. 8 world units tall seems to be a magic number, is that the unit size of the collider grid or something?
Observed Result: Fluid going mental