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Keyframing Vertex Mass in Cloth Simulation doesn't have any effect
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Description

System Information
Operating system: Windows-10-10.0.21370-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 470.25

Blender Version
Broken: version: 2.92.0, branch: master, commit date: 2021-02-24 16:25, hash: rB02948a2cab44
Worked: I can't find if it ever worked

Short description of error
Keyframing a vertex mass change does not affect the simulation; only the weight at the start affects the simulation. pausing the simulation and manipulating vertex mass works as expected however; the new mass applies to the target and it deforms differently. I've illustrated this with a pin group below, but it still occurs without a pin group, when colliding with a plane instead. It also happens on 3.0.0.

Exact steps for others to reproduce the error

  1. Create an icosphere with 3 divisions
  2. add the top 6 vertices to a vertex group "cloth pin target" with a weight of 1
  3. create a cloth simulation on the icosphere
  4. add "cloth pin target" as pin shape to cloth simulation
  5. keyframe vertex weight - eg 2kg on frame 50, 10kg on frame 90
  6. run simulation

I've attached this example file below:

I would very much like this to work, but I realize it may have not been intended to work like this. It's confusing that I'm able to set the keyframes if that is the case.

Thank you!