Is it possible to render a Fragment Shader asynchronously? about flutter HOT 4 CLOSED

The fragment shader execution is already "asynchronous" in that it runs on the GPU timeline, whereas the UI and raster threads are on the CPU timeline. however, if the execution of the shader workload is expensive enough you will find that it will essentially hog the GPU preventing the raster thread from being able to submit workloads, which in turn prevents the raster workload from finishing. This is the limit of splitting up work across threads: you can't increase access of shared resources like disk, network, GPU, et cetera.

Its also possible that certain laptops are falling back to Skia software rendering due to lack of hardware support. I couldn't tell you if this is the case from the information here, but if it was there would be little we could do.

So now I'm looking for alternative solutions. The first thing I tried is limiting the framerate of the background through the ShaderPainter.shouldRepaint method, but due to the high render time this had negligible impact.

That isn't what that method does. It only controls if the paint method is called. If that shader is used in a scene that is included in any part of a frame, whether or not the painter painted or the widgets rebuilt, it gets executed. The only way to limit how often it runs is to cache the rendered results to a texture (see SnapshotWidget for an example of how to do that).

In general, I would recommend designing your application to support the target hardware you want to support. If older laptops are important, then your app/game/et cetera needs to cut costs. You can do that by simplifying the shader, or reducing the amount of work done by reducing the size of the painter. Or find a mechanism to detect older hardware (Android API level?) and substitute a reduced quality effect.

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Oh, if you're running with Skia - you're probably getting some of the SnapshotWidget behavior automatically via raster caching. But that will only get you so far, as once you have to repaint you'll drop the frame again (one of the reasons automatic raster caching is a bad idea)

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This was informative. Thank you!

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