Optix realtime denoiser progressively reduces brightness of very bright objects. #76947

New Issue

Tober · 2020-05-21T22:22:56+02:00

Tober commented

2020-05-21 22:22:56 +02:00

System Information
Operating system: Windows 10
Render card: RTX 2080
Driver version: 445.87

Blender Version
Broken: 2.90.2 alpha

Short description of error
The realtime denoiser cumulatively reduces the brightness of pixels that are very bright before exposure calculations, causing pixels that should be white to turn grey under some exposures.

Exact steps for others to reproduce the error
Create a new "General" file
Set the Render Engine to Cycles.
Set the Viewport samples to 1000
Set the Viewport Denoising to "OptiX AI-Accelerated"
Set the Color Management Exposure value to -10
Set the default light to "Sun", keeping its strength at 1000
Set the Viewport shading mode to "Rendered"

As the number of samples rises, the cube becomes much darker in a number of discrete steps. The two lit faces of the cube, which start out as different shades, are reduced to the same shade of grey.

This does not happen when the denoiser is not applied.

The effect, on my machine, seems to first happen around 300 samples into the 1000 samples in the example file. However, if I set the sample count to ~100, let the viewport render all samples, and then increment the sample count by 1, it immediately triggers a step of the darkening.

Viewport left to render to 100 samples in one go:

Viewport after incrementing to 101 samples immediately after:

optix bug.blend

**System Information** Operating system: Windows 10 Render card: RTX 2080 Driver version: 445.87 **Blender Version** Broken: 2.90.2 alpha **Short description of error** The realtime denoiser cumulatively reduces the brightness of pixels that are very bright before exposure calculations, causing pixels that should be white to turn grey under some exposures. **Exact steps for others to reproduce the error** Create a new "General" file Set the Render Engine to Cycles. Set the Viewport samples to 1000 Set the Viewport Denoising to "OptiX AI-Accelerated" Set the Color Management Exposure value to -10 Set the default light to "Sun", keeping its strength at 1000 Set the Viewport shading mode to "Rendered" As the number of samples rises, the cube becomes much darker in a number of discrete steps. The two lit faces of the cube, which start out as different shades, are reduced to the same shade of grey. This does not happen when the denoiser is not applied. The effect, on my machine, seems to first happen around 300 samples into the 1000 samples in the example file. However, if I set the sample count to ~100, let the viewport render all samples, and then increment the sample count by 1, it immediately triggers a step of the darkening. Viewport left to render to 100 samples in one go: ![optix-100.jpg](https://archive.blender.org/developer/F8546816/optix-100.jpg) Viewport after incrementing to 101 samples immediately after: ![optix-101.jpg](https://archive.blender.org/developer/F8546818/optix-101.jpg) [optix bug.blend](https://archive.blender.org/developer/F8546822/optix_bug.blend)

Tober commented

2020-05-21 22:22:56 +02:00

Added subscriber: @Tober-1

Alaska commented

2020-05-22 05:50:14 +02:00

Added subscriber: @Alaska

Alaska commented

2020-05-22 05:50:14 +02:00

I am able to confirm in Blender 2.83 8a8c61190b (2020-05-21 13:03) and 2.90 8f21f867e7 (2020-05-21 21:20) on Linux with a GTX 1050Ti driver 440.82 running with the lauch command CYCLES_OPTIX_TEST=1 so I can get OptiX denoiser to run on my GPU.

I am able to confirm in Blender 2.83 `8a8c61190b` (2020-05-21 13:03) and 2.90 `8f21f867e7` (2020-05-21 21:20) on Linux with a GTX 1050Ti driver 440.82 running with the lauch command `CYCLES_OPTIX_TEST=1` so I can get OptiX denoiser to run on my GPU.

Brecht Van Lommel commented

2020-05-22 13:57:42 +02:00

Added subscriber: @pmoursnv