Unity Issue Tracker - Compute Shader GPU Readback is incorrect when using an integrated GPU

Won't Fix

Votes

2

Found in

2021.3.22f1

2022.2.13f1

2023.1.0b9

2023.2.0a8

Issue ID

UUM-31738

Regression

No

Compute Shader GPU Readback is incorrect when using an integrated GPU

Mar 28, 2023

How to reproduce:
1. Change the Editor’s used GPU to the integrated GPU
2. Open the "Integrated_GPU" project
3. Open the "Main" scene
4. Enter Play Mode and observe the Console

Expected result: Console prints "GPU Readback at position (1,1) Expected = WOOD (9) Actual: WOOD (9)"
Actual result: Console prints "GPU Readback at position (1,1) Expected = WOOD (9) Actual: NONE (0)"

Reproduced with: 2021.3.22f1, 2022.2.13f1, 2023.1.0b9, 2023.2.0a8
Could not test with: 2020.3.46f1 (could not resolve scripting errors)

Reproduced on: Windows 11
Not reproduced on: macOS Ventura 13.0 (M1)

GPU reproduced with:
Intel(R) Core(TM) i9-11900H @ 2.50GHz, 2496 Mhz, 8 Core(s), 16 Logical Processor(s) → Intel(R) UHD Graphics
Intel(R) Core(TM) i5-9400 CPU @ 2.90GHz: 6 cores 2904hz → Intel(R) UHD Graphics 630 Intel Direct3D 11.0 (by reporter)
Intel(R) Core(TM) i5-7267U CPU @ 3.10GHz: 4 cores 3096hz → Intel(R) Iris(R) Plus Graphics 650 Intel Direct3D 11.0 (by reporter)
Intel(R) Core(TM) i3-10110U CPU @ 2.10GHz: 4 cores 2592hz → Intel(R) URD Graphics Intel Direct3D 11.0 (by reporter)

GPU not reproduced with:
NVIDIA GeForce RTX 3050 Ti Laptop GPU
Apple M1

Notes:
1. To force the Unity Editor to use an integrated GPU on Windows 11: Start > Settings > Display > Graphics > Unity Editor / “Unity.exe” (make sure that you select the version you will open the project with) > Power Saving > Save
2. When forcing the Unity Editor to use a dedicated GPU, the Console will log the expected result
3. Also reproduced in Player

Resolution Note:

In the ComputePixelShaderController.cs, the user script writes:

const string outputBufferKey = "outputBuffer";
const int pixelTypeStride = 4;
outputBuffer = new ComputeBuffer(map.gpuOutput.Length, pixelTypeStride);
In Unity Doc from ComputeBuffer , it is mentioned that "On the shader side, ComputeBuffers with default ComputeBufferType map to StructuredBuffer<T> and RWStructuredBuffer<T> in HLSL."

Therefore, in the compute shader, they must use RWStructuredBuffer instead of RWBuffer. This is a user script error.

Comments (4)

cchute

Jul 18, 2023 20:52

Don't you think this warrants a shader compiler warning?

It's these type of platform specific traps, combined with poor documentation, that makes Unity a nightmare to work with.
cchute

May 22, 2023 16:40

Hello Unity is there any updates on this? Please resolve my business is crippled until this gets fixed
cchute

Mar 31, 2023 01:50

Good to see it is under consideration 2021.3.X!

Please consider making this a priority. This is not a cosmetic bug or something that can be worked around. Any game that relies on Compute Shaders is 100% broken for these users as they cannot get any compute results back to the GPU.

This is absolutely game breaking, and just leads to bad reviews for myself and less trust in Unity from the player base.

Please resolve ASAP
cchute

Mar 29, 2023 12:48

Hello!

Any idea when this might get fixed? We have a game in early access and this bug is crushing our fanbase. A loose timeline would be much appreciated so we can plan our release and stop having to tell everyone "It's a Unity bug we're waiting on them to fix it"

Thanks

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