Regression: Cycles Nishita Sky Texture causes fireflies under certain conditions #106706

New Issue

Alaska · 2023-04-08T09:43:23+02:00

Alaska commented

2023-04-08 09:43:23 +02:00

System Information
Operating system: macOS-13.3-arm64-arm-64bit 64 Bits
Graphics card: Metal API Apple M1 Pro 1.2

System Information
Operating system: Windows-10-10.0.22621-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 531.41

Blender Version
Broken version: 3.6.0 Alpha, branch: main, commit date: 2023-04-07 21:40, hash: e369bf4a6d38
Broken version: 3.5.0, branch: blender-v3.5-release, commit date: 2023-03-29 02:56, hash: 1be25cfff18b
Worked: 3.4

Testing points to 05bdef7ce6 as being the culprit commit.

Short description of error
Under certain conditions, the Nishita sky texture causes fireflies.
The conditions that impact it are:

Rendering backend (CPU or GPU)
Nishita sky texture sun angle
Nishita sky texture sun size
Total sample count

Exact steps for others to reproduce the error

Create a scene with a plane and give it a dark material.
Change the render engine to Cycles.
Add a Nishita Sky Texture to the world shader.
Change the pixel size for the Cycles viewport if you are using viewport rendering to test this. Changing the pixel size does not effect the issue, it just makes it easier to see since the pixels are bigger. This setting is found in Render Properties -> Performance -> Viewport -> Pixel Size
Start changing settings until you get fireflies.

Here's an example that works on my Mac:

Sun Size: 0.545° (Default)
Sun Elevation: 15° (Default)
Sun Rotation: -0.2°
Max Sample Count: 1024 Samples
Render Device: GPU (Metal)

Here is a copy of that scene.
Sky Texture Fireflies issue.blend

Here is an example of the fireflies. Left is using all the settings listed above, Right is using the same settings, but the Sun Rotation is -0.1°:

Settings above (Has fireflies)	`Sun Rotation: -0.1°`

Note 1: Most sun rotation and elevations combinations don't show this issue. For example, changing the Sun Rotation to -50.1° removes the fireflies.

Note 2: Different combinations of settings may produce fireflies on some devices and not others. For example, Sun Elevation: 15° and Sun Rotation: 8.5° produces fireflies for an RTX 4090 on Windows with CUDA and OptiX. But it does not produce fireflies on my Mac with Metal.

Note 3: Changing the Max Sample Count can impact how the fireflies form. For example, if the Max Sample Count is 1024, then lots of fireflies may form in the first 128 samples. But if the Max Sample Count is 128, no fireflies may form. Or if the Max Sample Count is 4096, fire flies only start forming after the first 800 samples.

I have also attached a video show casing the issue.

**System Information** Operating system: macOS-13.3-arm64-arm-64bit 64 Bits Graphics card: Metal API Apple M1 Pro 1.2 **System Information** Operating system: Windows-10-10.0.22621-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 531.41 **Blender Version** Broken version: 3.6.0 Alpha, branch: main, commit date: 2023-04-07 21:40, hash: `e369bf4a6d38` Broken version: 3.5.0, branch: blender-v3.5-release, commit date: 2023-03-29 02:56, hash: `1be25cfff18b` Worked: 3.4 Testing points to 05bdef7ce6 as being the culprit commit. **Short description of error** Under certain conditions, the Nishita sky texture causes fireflies. The conditions that impact it are: * Rendering backend (CPU or GPU) * Nishita sky texture sun angle * Nishita sky texture sun size * Total sample count **Exact steps for others to reproduce the error** 1. Create a scene with a plane and give it a dark material. 2. Change the render engine to Cycles. 3. Add a Nishita Sky Texture to the world shader. 4. Change the pixel size for the Cycles viewport if you are using viewport rendering to test this. Changing the pixel size does not effect the issue, it just makes it easier to see since the pixels are bigger. This setting is found in `Render Properties -> Performance -> Viewport -> Pixel Size` 5. Start changing settings until you get fireflies. Here's an example that works on my Mac: * Sun Size: 0.545° (Default) * Sun Elevation: 15° (Default) * Sun Rotation: -0.2° * Max Sample Count: 1024 Samples * Render Device: GPU (Metal) Here is a copy of that scene. [Sky Texture Fireflies issue.blend](/attachments/410ec426-adf5-4464-b2ed-9aef2d2a7103) Here is an example of the fireflies. Left is using all the settings listed above, Right is using the same settings, but the Sun Rotation is -0.1°: | Settings above (Has fireflies) | `Sun Rotation: -0.1°` | | -------- | -------- | | ![-0.2d.png](/attachments/2b9ec891-9f4a-40c8-b61c-f6de1b7bd49c) | ![-0.1d.png](/attachments/022088c3-7304-4b28-9a83-d05e78e432ef)| Note 1: Most sun rotation and elevations combinations don't show this issue. For example, changing the Sun Rotation to -50.1° removes the fireflies. Note 2: Different combinations of settings may produce fireflies on some devices and not others. For example, `Sun Elevation: 15°` and `Sun Rotation: 8.5°` produces fireflies for an RTX 4090 on Windows with CUDA and OptiX. But it does not produce fireflies on my Mac with Metal. Note 3: Changing the Max Sample Count can impact how the fireflies form. For example, if the Max Sample Count is 1024, then lots of fireflies may form in the first 128 samples. But if the Max Sample Count is 128, no fireflies may form. Or if the Max Sample Count is 4096, fire flies only start forming after the first 800 samples. I have also attached a video show casing the issue.

-0.2d.png

1.1 MiB

-0.1d.png

1.1 MiB

Sky Texture Fireflies issue.blend

890 KiB

Demonstration of Fireflies issue.mp4

5.8 MiB

Alaska added the

labels 2023-04-08 09:43:23 +02:00

Alaska changed title from ~~Cycles Nishita Sky Texture causes fireflies under certain conditions~~ to Regression: Cycles Nishita Sky Texture causes fireflies under certain conditions

2023-04-08 14:30:17 +02:00

Pratik Borhade commented

2023-04-10 08:25:51 +02:00

Hi, thanks for the report and bisecting. I can confirm.