Large soft shadows converge to an incorrect result in EEVEE viewport. #96623

New Issue

Alaska · 2022-03-19T01:37:35+01:00

Alaska commented

2022-03-19 01:37:35 +01:00

System Information
Operating system: Linux-5.16.0-3-amd64-x86_64-with-glibc2.33 64 Bits
Graphics card: NVIDIA GeForce RTX 3060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 510.54

Blender Version
Broken version: 3.2.0 Alpha, branch: master, commit date: 2022-03-17 21:23, hash: 6d97a5f93c
Broken version: 3.1
Broken version: 3.0
Broken version: 2.93
Broken version: 2.92
Broken version: 2.91
Broken version: 2.90
Broken version: 2.83
Broken version: 2.82
Broken version: 2.81
Broken version: 2.80

Short description of error
When rendering large soft shadows in the EEVEE viewport, it converges to an incorrect result at high sample counts. Here are some examples:


EEVEE viewport - 512 samples ("Mostly Normal")	EEVEE viewport - 16,384 samples ("Broken")	EEVEE final render (`F12`) - 16,384 Samples (To be used for comparison)

Exact steps for others to reproduce the error

Start with the default scene.
Add a ground plane. ({nav Add > Plane} then scale it up and shift it below the cube)
Select the default light and change it's radius to 2m
Render the scene in EEVEE to a high sample count in the viewport. This can be done by setting the EEVEE viewport sample count to something like 16,384 and letting it process.
Render the same scene in EEVEE with a final render (F12) and the same sample count and compare it to the viewport result. Notice that it's very different.

Note: Soft shadows is enabled by default in EEVEE in modern versions of Blender. But depending on your defaults, you might have to enable it. It's in {nav Render Properties Editor > Shadows > Soft Shadows}

**System Information** Operating system: Linux-5.16.0-3-amd64-x86_64-with-glibc2.33 64 Bits Graphics card: NVIDIA GeForce RTX 3060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 510.54 **Blender Version** Broken version: 3.2.0 Alpha, branch: master, commit date: 2022-03-17 21:23, hash: `6d97a5f93c` Broken version: 3.1 Broken version: 3.0 Broken version: 2.93 Broken version: 2.92 Broken version: 2.91 Broken version: 2.90 Broken version: 2.83 Broken version: 2.82 Broken version: 2.81 Broken version: 2.80 **Short description of error** When rendering large soft shadows in the EEVEE viewport, it converges to an incorrect result at high sample counts. Here are some examples: |![EEVEE Viewport Soft Shadows - 512 Samples.png](https://archive.blender.org/developer/F12933841/EEVEE_Viewport_Soft_Shadows_-_512_Samples.png)|![EEVEE Viewport Soft Shadows - 16384 Samples.png](https://archive.blender.org/developer/F12933843/EEVEE_Viewport_Soft_Shadows_-_16384_Samples.png)|![EEVEE Final Render Soft Shadows - 16384 Samples.png](https://archive.blender.org/developer/F12933845/EEVEE_Final_Render_Soft_Shadows_-_16384_Samples.png)| | -- | -- | -- | |EEVEE viewport - 512 samples ("Mostly Normal")|EEVEE viewport - 16,384 samples ("Broken")|EEVEE final render (`F12`) - 16,384 Samples (To be used for comparison)| **Exact steps for others to reproduce the error** 1. Start with the default scene. 2. Add a ground plane. ({nav Add > Plane} then scale it up and shift it below the cube) 3. Select the default light and change it's radius to `2m` 4. Render the scene in EEVEE to a high sample count in the viewport. This can be done by setting the `EEVEE viewport sample count` to something like 16,384 and letting it process. 5. Render the same scene in EEVEE with a final render (`F12`) and the same sample count and compare it to the viewport result. Notice that it's very different. Note: Soft shadows is enabled by default in EEVEE in modern versions of Blender. But depending on your defaults, you might have to enable it. It's in {nav Render Properties Editor > Shadows > Soft Shadows}

Alaska commented

2022-03-19 01:37:35 +01:00

Added subscriber: @Alaska

Philipp Oeser commented

2022-03-21 10:31:48 +01:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2022-03-21 10:31:48 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Philipp Oeser commented

2022-03-21 10:31:48 +01:00

Can confirm.

Clément Foucault commented

2022-05-10 15:09:12 +02:00

Added subscriber: @fclem

Clément Foucault commented

2022-05-10 15:09:12 +02:00

This is because we use a lower bitdepth for our accumulation buffers to save memory when rendering in viewport. At some points, the rounding introduced at the storage step gets noticeable. You can notice it also affects the antialiasing.

We might consider switching to a higher bitdepth if the final sample count is high but it would be weird to have this implicit change of behavior. Unless there is a way to avoid this rounding error but I am not aware of any.

This is because we use a lower bitdepth for our accumulation buffers to save memory when rendering in viewport. At some points, the rounding introduced at the storage step gets noticeable. You can notice it also affects the antialiasing. We might consider switching to a higher bitdepth if the final sample count is high but it would be weird to have this implicit change of behavior. Unless there is a way to avoid this rounding error but I am not aware of any.

Philipp Oeser removed the

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Large soft shadows converge to an incorrect result in EEVEE viewport. #96623