Good day,

I have been encountering an issue in Blender for some time and the issue remains with Blender 4.0. I'm not sure if it's the result of my error, as occasionally removing and adding physics properties fixes the problem, but in this case nothing I do fixes the issue.

In the attached Blend files below, I added Rigid Body physics to simulate 4 cannons firing at a target simultaneously. For 31 versions of this project (I incrementally saved each modification out of habit), nothing seemed to be out of the ordinary. It wasn't until I reached the 32-34 versions where I started noticing that the physics seemed to have completely frozen. At first I simply removed the Rigid Body properties from every simulated object and then added them back. This worked for version 32, but when I tried the same thing with version 34, nothing changed. Because I thought the simulation was close to complete for this small project, I primarily focused on adding simple shading, hence why I had not checked to see if the physics worked with 33, and saved 34 with the bug uncaught.

Feel free to test the .blend file and if you know of a way to correct this issue I would be very grateful if you could share with me what I did wrong (as I have seen this problem before in other blend files).

Thank you very much.

Here are the attached .blend files using blend-exchange (edited in as I had to use the question url to upload the files):

Working older version 31: Newer broken version 34:

  • $\begingroup$ Hello, could you please describe what the simulation is supposed to be exactly? (with the names of the objects) $\endgroup$
    – moonboots
    Commented Nov 18, 2023 at 8:57
  • $\begingroup$ Select the balls and move them out of their individual collections and in the Scene Collection. BTW, you have two overlapping balls in one of the cannons. $\endgroup$ Commented Nov 18, 2023 at 10:29
  • $\begingroup$ Hello @moonboots, the simulation is supposed to use the piston (Piston Ramming Rod) to launch the balls (simply named ball in each Canon collection) from each canon (Canon Body) and collide with the soft-body target (Cube, modified default cube) in the center of the platform (Floor). Because they are all supposed to launch simultaneously, I was curious to see what the target would do in respond to the collision from all sides. In 'Canon Box31.blend', the balls should collide with the target and cause it to spin. $\endgroup$ Commented Nov 18, 2023 at 14:15
  • $\begingroup$ @RumenBelev Thank you very much, this seems to have fixed the issue. I also deleted the overlapping balls, as Blender had duplicated each Rigid Body object and automatically dumped it in the Scene Collection. It's running smoothly now and I also noticed that I added the Room (named Cube.001) to a Canon collection. Putting it in the Scene Collection got it to run easily, so that advice helped a ton. I am going to try this with another Blender project with broken physics and see if the problem/solution is the same. Thank you again! If you had answered this as a solution. I'd give it a checkmark! $\endgroup$ Commented Nov 18, 2023 at 14:46


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