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Particle simulation doesn't work after adding a texture to the particle system
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Description

This is with the latest daily build (2017-07-21 a27b6ae), also happened on earlier dailys (2017-06-24 or something) not tested with older builds. Might be a regression.

As soon as you add a texture to a particle simulation, the simulation no longer works.

Steps to reproduce:

  • Create a plane, add a particle system, set it to hair
  • Enable Hair Dynamics
  • Add a Force Field (I used Wind blowing in Y direction)
  • Hit Alt-A to play, the Hair bows in Y direction as expected
  • On the particle system, add a texture, use a b/w image texture and set its influence to length+density
  • Hit Alt-A again, the Hair no longer moves

This can be worked around by baking a setting without the texture, and afterwards adding the texture back in.

I can of course upload a sample project, but this bug is so easy to reproduce that I don't think that's necessary.
I hope this problem hasn't been submitted yet, I didn't find it if it has.

Event Timeline

Yes. It is an already reported problem. Not really a bug but a known limitation.

Particles can be emitter or hair ; Influence panel in Textures tab will be the same for both types.

Settings under General label like Density are requiring physics behaviour baked for hair.
But you can use a texture for Length or settings under Hair or Physics labels with hair dynamics.

This might not be the right place to discuss. However, I don't really understand this:
If you have added a texture to a particle (hair) system, and you hit 'Bake', you get an 'empty bake', that is a simulation doing nothing. Ignoring all fields you have added. Without any warning or notice, that you have to remove the texture again before you can get a usable result. To be more clear, you get an 'erroneous result' without any hint why. This is considered a limitation?

As I see it, an error message describing this behavior would be the least thing to do. Even better would be to temporarily disable textures during baking and enable them again afterwards. On the other hand, I don't really understand why the baking process doesn't just ignore textures it can't handle.