PhotonDust - new particle system testing - Phase 3 (legacy removal)

[Frooxius]

Hello everyone!

I've added a third and final phase of testing PhotonDust! This will be the last phase, I want to give it a bit of a test in pre-release to make sure the removal of legacy system didn't break anything:

• Phase 1 - stability testing (this one is done!)
• Phase 2 - compatibility testing (this is pretty much done!)
• Phase 3 - legacy removal

This testing is for Phase 3

Build Version

2025.2.14.435

What is being tested

As part of our performance optimizations, we are replacing the existing (now called "Legacy") particle system in Resonite with our custom one called PhotonDust.

The legacy particle system is a hybrid between Unity and FrooxEngine, with Unity handling most of the simulation. This tight integration prevents moving FrooxEngine from being moved out of Unity into a more performant .NET 9 process. PhotonDust solves this problem, by handling most parts of the simulation completely within FrooxEngine and only submitting simulated results to Unity for rendering.

Since this introduces a new complex system to Resonite, this has potential to cause stability issues (though most were eliminated during development itself) and content compatibility issues - our system works on different principles from the original particle system - it is a lot more modular and flexible. This requires adapters to support existing content.

You can learn a bit more about PhotonDust here:
#587

General testing notes

• Legacy particle system is now completely gone
• Setting to enable the conversion is gone
• Any legacy particle items are automatically converted to PhotonDust on spawn/load

Avoiding data corruption

• DO NOT save any converted worlds/items for any purpose other than testing - they might break or have conversion issues!

How to test

In the Phase 3 we're just doing last checks to make sure everything is squared away before it gets merged to main and that removing the legacy particle system didn't break anything - and that we didn't forget bits.

There's also few compatibility items that got resolved now, which explicitly requires the old system to be removed.

The testing is done on prerelease branch, because once it's merged in, you won't have a choice but to have everything in PhotonDust.

• On Steam, switch to the prerelease branch and make sure the build updates before you run it
• Make sure your build version matches the one at the top of this message

What to test

• Spawn items, load worlds, make sure that particle systems work properly and aren't broken
• Check if any behaviors are broken - e.g. any ProtoFlux that interacts with particles or any components:
  -- ParticleSpray tool
  -- ViolentAprilFoolsExplosion
  -- Brushes with particle systems
• You can check for compatibility and see if things look as they used to (or very close) - but that was major focus of phase 2 which allowed side-by-side comparison

What to watch out for

These are good things to watch out for when testing the new particle system:

• Converted particle systems and related components/flux behaving differently from unconverted or being broken
• Sessions crashing
• Client crashing
• Freezing or locking up

What NOT to test & report

• Generally things that do not involve this system - any existing unrelated bugs with components and other systems.
  -- If you're unsure, try to replicate the issue on the main build and see if it also occurs - if it also happens there, just report it as normal bug

If you find something that got broken

• Create a GitHub issue for a pre-release bug: https://github.com/Yellow-Dog-Man/Resonite-Issues/issues/new?assignees=shiftyscales&labels=prerelease&projects=&template=prerelease.yml
• Make sure to include the log
• Please include description of what happened. Be succinct, but exact.

IMPORTANT: For compatibility issues

• Try to isolate where is the difference in behavior coming from as much as you can in the report
• Make sure to include screenshots/video of both unconverted & converted behavior
• Please provide us ONLY unconverted copy of the item for testing
• You can strip down the item to just the minimum particle system that still replicates the issue (in fact, this is preferable!):
  -- Strip the unconverted item down as much as possible
  -- Save the stripped down item to your inventory
  -- Turn on conversion
  -- Check if the issue still persists on the converted item

If you find that stuff works okay

Please report it too and include details on what you generally tested, so we know things are okay. You don't need to make a new issue for this - just a comment in this Discussion is fine.

This lets us know that a bunch of stuff was tested and get better confidence that stuff won't break with release.

How long will testing go for?

This depends on how much is broken. However since Phase 2 ran for almost two months, majority of compatibility and stability issues should be resolved at this point and this is more just checking if anything breaks with the full removal of legacy system.

IMPORTANT: This is now planned to be merged this upcoming Monday!

[Nytra]

Using Beta 2025.2.5.1304

In Lexevo's Particle Exhibition world (resrec:///U-Lexevo/R-8599fdfa-2af6-422f-981a-0db077c8e514), Exhibit 3's firework particle emits differently

The explosion particles emit like a sphere in legacy, but they emit like a cylinder in PhotonDust

It does use a CylinderEmitter so I'm not sure why it looks spherical in the legacy one

Folder with the explosion particle (unconverted): resrec:///U-Nytra/R-F90BFED578BC34D23F369D5273843ADFD84D71D80E280543F2F072A82436250E

[shiftyscales]

If you haven't already- can you please create a separate prerelease issue for tracking this and provide logs there, @Nytra?

In the reporting steps listed above, that is a requirement.

[Nytra]

Done here #3699

[Frooxius]

[PRE-RELEASE] 2025.2.10.1338
Update to the prerelease channel build for removing the Legacy Particle system! This should fixup both reported issues.

Just a reminder - the Legacy Particle system will be removed very soon, probably this week, so please give this a test if you can, so we can wrap things up and move to the next phase of performance update.

Fixes:

• Fixed dash emitting particles when in desktop mode (based on report by @troyBORG, issue RadiantDash PhotonDust rendering in desktop, far away? #3678)
• Fixed legacy CylinderEmitter that is emitting from the cylinder volume not emitting in the same direction after conversion (reported by @Nytra, issue [PhotonDust Compatibility] Converted CylinderEmitter looks different from legacy #3699)

[Frooxius]

[PRE-RELEASE] 2025.2.12.1288
This build contains the same changes as 2025.2.12.1266 above, but with the removal of the legacy particle system.

Just a reminder - the Legacy Particle system will be removed very soon, probably this week, so please give this a test if you can, so we can wrap things up and move to the next phase of performance update.

Fixes:

• Added validation to Min/Max sequence count for SequenceRibbonSplitter (based on report by @Nytra, issue [PhotonDust] SequenceRibbonSplitter: Setting MinSequenceCount to be greater than MaxSequenceCount breaks all PhotonDust systems in the world #3663)
  -- This prevents invalid values from breaking PhotonDust
  -- If MinSequenceCount is larger than MaxSequenceCount, then it'll be always used
• Fixed regression causing TrailLifetimeFromSizeInitializer module being always on for converted trails, resulting in incorrect lengths (reported by @ModernBalloonie, issue Converted trails for the teleporter in the tutorial world are not as long as they should be. #3701)
• Fixed ConeEmitter not respecting DirectionTransformMode for RadialUniform directions, resulting in different particle velocities for legacy content (based on report by @Nytra, issue [PhotonDust Compatibility] Converted smoke particles appear much bigger #3705)
• Fixed trails from legacy particle systems having slightly different color when using Min/Max trail color (reported by @Krzeszny, @Joshtiger, issue [PhotonDust] Converted particles look brighter (have more bloom?) #3488)
  -- This is due to legacy system converting those colors as Linear and then Unity particle system reinterpreting them as sRGB
• Fixed legacy particle systems with render transform override that are scaled to zero by default not rendering after conversion (based on report by @badhaloninja, issue PHOTONDUST Particles do not respect RenderTransformOverride #3531)
  -- This is done by disabling the UseSystemLocalScale when this transform override is detected - with PhotonDust, the particle scaling is computed only once during simulation - render transform override cannot update the individual particle sizes

[orange3134]

I checked again with [PRE-RELEASE] 2025.2.12.1288 for a previously resolved issue and it appears to be recurring.
Video and logs regarding the issue have been reported here.

#3301 (comment)

#3381 (comment)

[NukiRaccoon]

My particle trails in Support Group Center turned purple and weird...

They were Black before...

This may be the result of an undefined or unsupported behavior: this was a placeholder I made right before testing PhotonDust, and I don't think I fully defined the trails in there.

Item Link...
resrec:///U-1NpQoxe8oee/R-5deffe93-afd1-465a-b65b-bbba6c8e37fa

[Nytra]

No trail material is set

[shiftyscales]

If there is no material set either prior or post-conversion, then I would consider that an expected result, @NukiRaccoon.

But regardless- per out testing instructions above we request users report issues via the prerelease template.

[Frooxius]

[PRE-RELEASE] 2025.2.13.1418
This build contains the same changes as 2025.2.13.1388 above, but with the removal of the legacy particle system.

Just a reminder - the Legacy Particle system will be removed this upcoming Monday! If you find any last minutes issues, please test and report them now!

New Features:

• Add debug statistics for particle state uploads (currently visible in the Debug dialog on the Worlds page)

Optimizations:

• Skip particle buffer submissions when the particle system is empty (based on report by @orange3134, issue Particles with significant performance degradation after conversion to PhotonDust #3301)
• Use separate processing queue for uploading particle simulation results for rendering to improve particle smoothness (based on report by @orange3134, issue Particles with significant performance degradation after conversion to PhotonDust #3301)
  -- This makes sure that the particle simulation results don't fight for processing time with other asset uploads (meshes, textures, materials...)
  -- The particle upload queue also has more time for processing. This means with heavy loads it can lower FPS at bit more (we can tweak how much), but will reduce jerkiness of particle systems in some conditions

[shiftyscales]

@orange3134 has discovered a fairly significant regression on 2025.2.13.1388 I would consider a blocker for Monday's planned release, @Frooxius.

#3726

[Frooxius]

It's been fixed!

[Frooxius]

[PRE-RELEASE] 2025.2.14.435
This build contains the same changes as 2025.2.14.417 above, but with the removal of the legacy particle system.

Just a reminder - the Legacy Particle system will be removed this upcoming Monday! If you find any last minutes issues, please test and report them now!

Fixes:

• Fixed trails not getting properly cleaned up when they don't die immediately with the particle (based on report by @orange3134, Mhowser, @dustysprinkles, @Krzeszny, issue Boot sound #3729)