My question is short: Is it possible, and if so how, to read a texture or framebuffer created by WebGPU in WebGL2?
I've googled, and the only thing I found is this bug: https://bugs.chromium.org/p/chromium/issues/detail?id=1200466, but I can't say, that i fully understand it, or where the documentation is.
The overall goal is to create a render engine in WebGPU, copy it to a WebGL texture and use it in a QML app compiled for WebAssembly. QML does not yet support WebGPU, and it's unclear when support will come.
There is no special interop between webgl and webgpu. In WebGL you can call texImage2D and pass it a canvas element. In WebGPU you can call copyExternalImageToTexture and pass it a canvas element. In both cases that can be a 2d canvas, a webgl canvas, a webgl2 canvas, a bitmap canvas or a webgpu canvas