The WebGPU graphics API provides powerful graphics features, however, it also has some limitations you need to be aware of:
There are a few limitations to compute shaderA program that runs on the GPU. More info
See in Glossary in Web.
You can use structured buffers, RWStructuredBuffer, but not RWBuffer in compute shaders.
Limited read-write storage texture formats
WebGPU only supports a very limited set of texture formatsA file format for handling textures during real-time rendering by 3D graphics hardware, such as a graphics card or mobile device. More info
See in Glossary for read-write storage textures in compute shaders. HLSL doesn’t explicitly state the access type of a storage texture, so it’s based on usage.
RWTexture2D<float> tex; // storage texture
tex[uv] = 1.0f; // write only
tex[uv] += 1.0f; // read-write
Write-only storage textures are generally much better supported. Refer to Texture format limitations.
With WebGPU, you must only call barrier functions from non-uniform blocks. Non-uniform blocks are shader code blocks that aren’t uniformly consistent across multiple threads of execution. If you call a barrier function from a non-uniform block, WebGPU will fail to compile.
The following are HLSL barrier functions:
* GroupMemoryBarrier
* GroupMemoryBarrirWithGroupSync
* DeviceMemoryBarrier
* DeviceMemoryBarrierWithGroupSync
* AllMemoryBarrier
* AllMemoryBarrierWithGroupSync
WebGPU doesn’t support async compute.
WebGPU doesn’t provide support for the following features:
Wave Intrinsics (WaveBasic, WaveVote, WaveBallot, WaveMath, WaveMultiPrefix)
QuadShuffle
Int64
Native16Bit
WebGPU doesn’t support synchronous readback of buffer or texture data from the GPU to the CPU. The following functions will not work:
Instead, use the AsyncGPUReadback API to read buffer or texture data from the GPU to the CPU. For screen captures, use ScreenCapture.CaptureScreenshotIntoRenderTexture along with AsyncGPUReadback.
For information about WebGPU texture format capabilities, refer to the W3 documentation on WebGPU. Some formats are more restrictive than on other APIs, particularly for storage texture usage.
For example, WebGPU doesn’t support RHalf as a storage texture format, which means if you do create a RenderTexture with that format, you must make sure enableRandomWrite is set to false (which is the default value). RFloat supports storage texture usage, so you can create an RFloat RenderTexture with enableRandomWrite, instead of RHalf.
You can use SystemInfo.GetCompatibleFormat to find a format that will work for a given usage.
The output type of a fragment shader must have a greater or equal number of channels as the target render textureA special type of Texture that is created and updated at runtime. To use them, first create a new Render Texture and designate one of your Cameras to render into it. Then you can use the Render Texture in a Material just like a regular Texture. More info
See in Glossary format.
If the RenderTexture is RGBA, it has 4 channels. The fragment shader must output a float4 or half4. If it returns a float or half, WebGPU will encounter an error because there are channels of the render texture that will be uninitialized.
If a RenderTexture is R8, it has 1 channel. The fragment shader can then output a float or half. The fragment shader can also return a float4 or half4, and the extra output channels will be ignored.
The number of textures you can access from a shader is limited to 16 on many platforms. This limit can easily be hit by the terrainThe landscape in your scene. A Terrain GameObject adds a large flat plane to your scene and you can use the Terrain’s Inspector window to create a detailed landscape. More info
See in Glossary renderer, particularly with layer textures. This can make terrain rendering problematic for WebGPU. It is recommended that you limit the number of terrain texture layers you use.