Is there any known implementation of a 2D canvas fallback for the awesome playcanvas game engine?
The idea is that the system should test rendering performance during the loading process in WebGL vs Canvas 2D, and fall back to Canvas 2D in case it finds better performance there o in cas WebGL is not supporte in the browser.
Other frameworks three.js or pixijs have this feature and it would be great for playcanvas, but as long as I have seen they do not have this feature and no solution have been implemented by the community.
No, there is no Canvas 2D fallback for PlayCanvas.
First of all, Canvas 2D will never be faster than WebGL for rendering 3D scenes. This is because you would have to shift complex GPU tasks onto the CPU. PlayCanvas implements a very sophisticated physical rendering pipeline and reimplementing it CPU-side will never give acceptable performance. It makes more sense for Pixi because Pixi is largely concerned with 2D sprite primitives which can be rendered quite cheaply by Canvas 2D.
At the time of writing, WebGL has a penetration of 91.1% and the trend is still upwards. Therefore, you have a relatively small minority of people who can't experience WebGL right now.
In the situation where the user can't run WebGL (for whatever reason, such as running IE9 and below), the recommendation would be to simply display a message asking to upgrade to a WebGL-capable browser.