Image sequence playhead for particle system textures never advances past first frame of sequence when particles are baked #92190

New Issue

Richard Martin · 2021-10-13T19:09:55+02:00

Richard Martin commented

2021-10-13 19:09:55 +02:00

System Information
Operating system: Windows 10/64
Graphics card: NVIDIA GeForce GTX 1060

Blender Version
Broken: 2.93, 3.0.0
Worked: n/a

Short description of error
When I create a particle system that relies on an image texture containing an image sequence to control density, the playhead for that image sequence remains "stuck" on the first frame of the image sequence when I bake the particle system, regardless of the output length of the composition. This is true regardless of what type of image sequence is used (i.e. frames in a container such as .mp4 or .mov, or sequences of images such as .exr, .tif, or .png) or what playback options for the sequence are set (i.e. Cyclic and Auto Refresh can both be checked; it won't matter).
Renders of an un-baked particle system using a moving texture to control particle density in Cycles are unusable.
Renders of an un-baked particle system using a moving texture to control particle density in Eevee are occasionally usable (although unreliable: one must make absolutely certain that no frames are cached before attempting a render).

Expected behavior
My expectation is that the playhead for an image sequence using a texture to control particle density would advance when the particle system is baked. It should appear both in stage preview and final rendered output that the source of particle emission appears to move, which is to say it should accurately track the black and white areas in the image sequence.

Exact steps for others to reproduce the error
Create an empty Blender stage;
Add a plane to the stage;
Create a texture based on any black-and-white-only image sequence (i.e. a white circle whose position changes with time, superimposed on a black frame); the sequence can be either containered-image or discrete-image;
Create a particle system for the plane;
Assign the texture to the particle system, leaving only the "Density" influence in the texture checked;
Move the stage playhead to frame 0 of the composition;
Click "Delete All Bakes" to clear any baked frames, also change number of particles in order to delete frames in memory;
Click Play on the stage;
Halo objects should be being emitted from the white areas in the texture as they move around in the texture (the emitter will appear to change position);
Move the stage playhead back to frame 0 of the composition;
Click "Delete All Bakes" to clear any baked frames;
Click "Bake All Dynamics" to bake the particles;
Click Play on the stage;

Steps done in following file:
particle-density-demo.rar

Both on the stage and in rendered output, particles will be emitted only from the location on the plane that corresponds to the white area as it was on the first frame of the image sequence.
And if someone could show me where in the code this stuff is handled, I'd be more than happy to take a look.

**System Information** Operating system: Windows 10/64 Graphics card: NVIDIA GeForce GTX 1060 **Blender Version** Broken: 2.93, 3.0.0 Worked: n/a **Short description of error** When I create a particle system that relies on an image texture containing an image sequence to control density, the playhead for that image sequence remains "stuck" on the first frame of the image sequence when I bake the particle system, regardless of the output length of the composition. This is true regardless of what type of image sequence is used (i.e. frames in a container such as .mp4 or .mov, or sequences of images such as .exr, .tif, or .png) or what playback options for the sequence are set (i.e. Cyclic and Auto Refresh can both be checked; it won't matter). Renders of an un-baked particle system using a moving texture to control particle density in Cycles are unusable. Renders of an un-baked particle system using a moving texture to control particle density in Eevee are occasionally usable (although unreliable: one must make absolutely certain that no frames are cached before attempting a render). **Expected behavior** My expectation is that the playhead for an image sequence using a texture to control particle density would advance when the particle system is baked. It should appear both in stage preview and final rendered output that the source of particle emission appears to move, which is to say it should accurately track the black and white areas in the image sequence. **Exact steps for others to reproduce the error** Create an empty Blender stage; Add a plane to the stage; Create a texture based on any black-and-white-only image sequence (i.e. a white circle whose position changes with time, superimposed on a black frame); the sequence can be either containered-image or discrete-image; Create a particle system for the plane; Assign the texture to the particle system, leaving only the "Density" influence in the texture checked; Move the stage playhead to frame 0 of the composition; Click "Delete All Bakes" to clear any baked frames, also change number of particles in order to delete frames in memory; Click Play on the stage; Halo objects should be being emitted from the white areas in the texture as they move around in the texture (the emitter will appear to change position); Move the stage playhead back to frame 0 of the composition; Click "Delete All Bakes" to clear any baked frames; Click "Bake All Dynamics" to bake the particles; Click Play on the stage; Steps done in following file: [particle-density-demo.rar](https://archive.blender.org/developer/F11069156/particle-density-demo.rar) Both on the stage and in rendered output, particles will be emitted only from the location on the plane that corresponds to the white area as it was on the first frame of the image sequence. And if someone could show me where in the code this stuff is handled, I'd be more than happy to take a look.

Richard Martin commented

2021-10-13 19:09:55 +02:00

Added subscriber: @Ariesboy571

Richard Antalik commented

2021-10-13 19:17:44 +02:00

Added subscriber: @iss

Richard Antalik commented

2021-10-13 19:17:44 +02:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Richard Antalik commented

2021-10-13 19:17:44 +02:00

Please upload simple .blend file with small image sequence you used that does demonstrate this issue.

Richard Martin commented

2021-10-14 00:13:13 +02:00

particle-density-demo.rar

This contains the .blend file, the .mov file, and the .exr files needed.

[particle-density-demo.rar](https://archive.blender.org/developer/F11069156/particle-density-demo.rar) This contains the .blend file, the .mov file, and the .exr files needed.

Richard Antalik commented

2021-10-14 20:22:56 +02:00

Changed status from 'Needs User Info' to: 'Confirmed'

Richard Antalik commented

2021-10-14 20:28:32 +02:00

Seems when you set texture influence to lifetime it kinda works, but I think effect is different than density influence.

I am not very familiar with particle system code, but I think particle_distribute.c or particle_system.c would be good start. Keep in mind, that this system is marked as EOL and it should be replaced by geometry nodes. That means, it is good idea to check with developers maintaining this module about fixing this, but I think this could be simple fix so it shouldn't be very problematic to review and accept.

Seems when you set texture influence to lifetime it kinda works, but I think effect is different than density influence. I am not very familiar with particle system code, but I think particle_distribute.c or particle_system.c would be good start. Keep in mind, that this system is marked as EOL and it should be replaced by geometry nodes. That means, it is good idea to check with developers maintaining this module about fixing this, but I think this could be simple fix so it shouldn't be very problematic to review and accept.

Dalai Felinto commented

2022-05-09 15:00:23 +02:00

Added subscriber: @dfelinto

Dalai Felinto commented

2022-05-09 15:00:23 +02:00

Marking this as known issue since it depends on the old particle settings which is end of life .

Marking this as known issue since it depends on the [old particle settings which is end of life ](https://developer.blender.org/tag/nodes_physics/).

Philipp Oeser removed the

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Image sequence playhead for particle system textures never advances past first frame of sequence when particles are baked #92190