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Maniphest T91922

Cycles X Particle Alpha
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Description

System Information
Operating system: WIN10
Graphics card: 3090FE

Blender Version
Broken: blender-3.0.0-alpha+master.34cf33eb1209-windows.amd64-release
Worked: blender 2.93.4

Short description of error
Particles are procedural emission plugged into volume. There appears to be some kind of alpha issue as they block the light emitted from other particles behind them.

CyclesXSunTest.blend125 MBDownload

Exact steps for others to reproduce the error
Attached is the blend file. Open in 2.93.4 and render, then open in 3.0 and render. It'll reproduce these attached images.

Revisions and Commits

rC Cycles
D12759rCe276f51f6f62 Fix T91922: Cycles artifacts with high volume nested level
rB Blender
D12759rBc6275da852ea Fix T91922: Cycles artifacts with high volume nested level

Related Objects

Event Timeline

Greg Ellingson (WhiteRoosterProductions) created this task.Oct 3 2021, 5:56 PM
Alaska (Alaska) changed the task status from Needs Triage to Confirmed.Oct 3 2021, 11:22 PM
Alaska (Alaska) added a project: Render & Cycles.
Alaska (Alaska) added a subscriber: Alaska (Alaska).

I can confirm.

The issue seems to be with objects intersecting each other. You can see the outline where they intersect which shouldn't be happening.

Sergey Sharybin (sergey) added a subscriber: Sergey Sharybin (sergey).EditedOct 5 2021, 11:40 AM

Simplified version of the file

CyclesXSunTest_Simple.blend1 MBDownload
.

Addition: The root cause is not big enough volume stack. For the ideal performance need to detect the volume nested depth at runtime, to keep the integrator state small.

Sergey Sharybin (sergey) claimed this task.Oct 5 2021, 11:57 AM
Sergey Sharybin (sergey) closed this task as Resolved by committing rBc6275da852ea: Fix T91922: Cycles artifacts with high volume nested level.Oct 6 2021, 3:59 PM
Sergey Sharybin (sergey) added a commit: rBc6275da852ea: Fix T91922: Cycles artifacts with high volume nested level.
Brecht Van Lommel (brecht) added a commit: rCe276f51f6f62: Fix T91922: Cycles artifacts with high volume nested level.Jan 27 2022, 11:29 PM