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Hair Particles not updating in Viewport when using Textures to drive Hair Size
Open, Confirmed, MediumPublic


System Information
Operating system: Darwin-16.7.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon R9 M295X OpenGL Engine ATI Technologies Inc. 4.1 ATI-1.51.8

Blender Version
Broken: version: 2.80 (sub 74), branch: blender2.7, commit date: 2019-06-16 23:08, hash: rB12da679fa094
Worked: (optional)

Short description of error
I used dynamic paint to create an image sequence texture, which I was using as a mask to drive hair growth size from the particle system. If I do it this way, things render out correctly, but I cannot see any hair particles inside the viewport, so its impossible to check my work before I render.

Exact steps for others to reproduce the error
-Create Plane and Cube, animate cube across plane
-Set Cube to Brush, Plane to Canvas with Dynamic Paint
-Brush Paint color White, canvas material Black
-Set canvas format to image sequence and bake it out
-Create hair particle system on Plane
-New Texture for Particle system, import create image sequence
-Set texture to drive size only

Now, if you change any of the hair settings, you cannot see the hair in the viewport and can only see upon export.

Event Timeline

This seems like a pretty long process to reproduce, can you attach a blend file demonstrating the issue?

Philipp Oeser (lichtwerk) claimed this task.
Philipp Oeser (lichtwerk) triaged this task as Confirmed, Medium priority.

This is reproducable with any image sequence mapped to ParticleSettings influence [no update on framechange there]

Testfile [including image sequence]:

Pretty sure there is a more "correct" way of solving this, but I added following relations [in case image is a sequence]

  • timesource -> texture (cow)
  • texture (cow) --> particle settings eval

[only got it to work using NodeType::COPY_ON_WRITE -- as I said this might be wrong, but otherwise I couldnt get the updates to show... see D5088]