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The collision modifier doesn't kill particles before the scene's start frame
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System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 960M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 465.89

Blender Version
Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-04-17 20:13, hash: rB8d30a7a1cf7b
Worked: It didn't work on 2.79

Short description of error
Particles that start before the scene's start frame aren't killed by objects with a collision modifier that is set to kill particles.

Exact steps for others to reproduce the error

  1. Add an object (A);
  2. Add a particle system to A;
  3. Add another object (B);
  4. Add a collision modifier to B;
  5. Set use_particle_kill to True on B's collision modifier;
  6. Set frame_start to a negative number on A's particle system;
  7. Move the objects so that the particles of A will eventually touch B before the scene's frame_start;
  8. Play the animation.

Event Timeline

Hi and thx reporting!

There is a way to make this work:

  • allow negative frames in Preferences > Animation
  • scrub to the (negative) startframe of your simulation (in your case -200)
  • bake simulation from there
  • collision should work in the negative range then as well

Of course this is less then ideal (it is a mere workaround), but this issue has been reported before, see T71075: Particle collisions aren't simulated before frame zero for negative frame simulations, will merge these reports.