Fireflies with Glossy Multiscatter GGX #50234

New Issue

Manuel Albert · 2016-12-12T18:12:18+01:00

Manuel Albert commented

2016-12-12 18:12:18 +01:00

System Information
Windows 10 and GTX980m

Blender Version
Broken: (example: 2.78 62a6ed9)

Fireflies with Glossy Multiscatter GGX

MultiscatterGGX.blend
1 Open the blenderfile
2 Render the file

Recently I noticed fireflies in my renders and wasn't sure where they came from as I used fairly high sample count (2048spp up to 8192spp), MIS, Filter Glossy 0.2 and had caustics turned off. I found that it's comming from high roughness values and glossy multiscatter ggx option. The fireflies do not appear with 'standard' GGX.
I am not sure if this is expected behavoir and hope it's a valid bugreport. When looking for informations I only found that multiscatter GGX tends to be noisier but nothing about fireflies.

**System Information** Windows 10 and GTX980m **Blender Version** Broken: (example: 2.78 62a6ed9) **Fireflies with Glossy Multiscatter GGX** [MultiscatterGGX.blend](https://archive.blender.org/developer/F417095/MultiscatterGGX.blend) 1 Open the blenderfile 2 Render the file Recently I noticed fireflies in my renders and wasn't sure where they came from as I used fairly high sample count (2048spp up to 8192spp), MIS, Filter Glossy 0.2 and had caustics turned off. I found that it's comming from high roughness values and glossy multiscatter ggx option. The fireflies do not appear with 'standard' GGX. I am not sure if this is expected behavoir and hope it's a valid bugreport. When looking for informations I only found that multiscatter GGX tends to be noisier but nothing about fireflies. ![mggx.png](https://archive.blender.org/developer/F417096/mggx.png)

Manuel Albert commented

2016-12-12 18:12:18 +01:00

Changed status to: 'Open'

Manuel Albert commented

2016-12-12 18:12:18 +01:00

Added subscriber: @ManuelAlbert

Sergey Sharybin commented

2016-12-13 12:44:08 +01:00

Added subscriber: @Sergey

Lukas Stockner was assigned by Sergey Sharybin

2016-12-13 12:44:08 +01:00

Sergey Sharybin commented

2016-12-13 12:44:08 +01:00

The code here is barely readable. Assigning to Lukas.

Lukas Stockner commented

2017-07-03 18:55:24 +02:00

Changed status from 'Open' to: 'Archived'

Lukas Stockner closed this issue

2017-07-03 18:55:24 +02:00

Lukas Stockner commented

2017-07-03 18:55:24 +02:00

Sorry for ignoring this report for so long...
These fireflies aren't really a bug, it's just a shortcoming of the stochastic evaluation used by the MultiGGX model.

It should be possible to get rid of them by implementing MIS-weighted bidirectional walks as described here which should be rather easy with the current code afaics, but that's a ToDo, not really a bug.

So, I'll close this for now, but I'll look into implementing the improved random walks.

Sorry for ignoring this report for so long... These fireflies aren't really a bug, it's just a shortcoming of the stochastic evaluation used by the MultiGGX model. It should be possible to get rid of them by implementing MIS-weighted bidirectional walks [as described here ](https://drive.google.com/open?id=0BzvWIdpUpRx_U0c0bWxVWUUwbTA) which should be rather easy with the current code afaics, but that's a ToDo, not really a bug. So, I'll close this for now, but I'll look into implementing the improved random walks.

Mohamed Sakr commented

2019-03-04 17:22:31 +01:00

Added subscriber: @MohamedSakr

Mohamed Sakr commented

2019-03-04 17:22:31 +01:00

Hey @LukasStockner , any idea when this one will get resolved?

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Fireflies with Glossy Multiscatter GGX #50234