Question WebGL clears frame after disabling camera

I'm looking to have WebGL keep the last rendered frame around (i.e. not get cleared) after the camera is disabled. I'm looking to save some rendering time, since for my application, there will be more idle time than dynamic camera time.

The thing is, in the Unity Editor and in a Windows Standalone build, it does exactly as I'd expect. The frame does not get cleared. It just hangs around. However, in WebGL, the frame is cleared.

Does anyone have any ideas for what I can do to prevent the last rendered frame from getting cleared?

 

How about saving the last frame into a texture and just keeping it on instead of RT rendering after it's disabled?

 

This is definitely my fallback option, but I was really hoping to not clear the last frame buffer, considering that would be the least expensive solution, especially since it already works for desktop/Unity editor.

This window is also resizable, so having to deal with a render texture can sometimes be a bit more work.

 

You haven't mentioned how you achieve that. I assume it's via Camera Clear Flags?
And URP or Legacy? You could try a test project with the other renderer to see if that allows not clearing the buffer.

And does the behaviour change in fullscreen?

I have a hunch that this is something OpenGL specific. One thing you can try is to go into Player Settings for Windows and disable Auto Graphics API and pick one of the OpenGL renderers as the topmost respectively only supported Graphics API to see if it won't work with desktop OpenGL either. At least it would confirm that this is something OpenGL specific.

 

Good point. My hunch is that it has to do with how WebGL constantly redraws within the canvas, thus why there are so many issues around window resize, scaling when building for it. But just a hunch at this point.

 

I didn't do anything. I just disabled the camera in LateUpdate(), and the image stays, I was just assuming at that point, the back and front buffer just contain the same image, and it's not getting cleared. The Camera Clear flags wouldn't be used in this scenario since the camera is disabled at that point.

I've since moved onto the RenderTexture solution, which I was expecting I'd have to do. So far, it's working okay. The 1920x1080 rendertexture is being written to fine, but since the background is transparent, I'm getting some hall of mirrors due to the backbuffer not getting cleared. Is there a way to clear the backbuffer independent of the camera doing it?


EDIT:
Oh yeah, for the Desktop standalone target, I switched from DX11 to OpenGL ES3, and I get the same results as DX11. Which is to say, NOT like WebGL.