Post processing example doesn't support resizing

[johanhelsing]

How can Bevy's documentation be improved?

The post_processing example doesn't currently support resizing. Its stated intent is to be:

useful to implement your own post-processing effect such as
edge detection, blur, pixelization, vignette... and countless others.

If people copy this code to their own projects it would be really nice if it properly supported resizing.

I think there may be two viable solutions to this:

1. Write a system that resizes the full screen quad whenever the window size changes
2. Write a custom vertex shader that takes the view.width and height uniform values into account and is always snapped to the edges of the viewport.

[mockersf]

I couldn't reproduce any issue with resizing, but after playing with values in the example a little more it's possibly due to having a 2x screen scale, and the mesh being sized with physical screen size. This should also be fixed.

[johanhelsing]

I's a bit subtle in the example because there is nothing near the edges of the screen. If you set a small initial size using WindowDescriptor and then scale the window up, you can see it more clearly, though.

[AndrewB330]

I just hit this problem and I couldn't figure out how to write this resizing system. From what I understand we need to resize render target image as well as the quad.

When I'm calling resize on the image I'm getting an error that "color" and "resolve" attachments have different sizes, and I can't understand why since attachments should be synced on the extract stage, right? And for the quad, I guess we should just create a new quad every time?

[johanhelsing]

I guess it's probably better to go the vetex shader route and let the quad always be of size (2.0, 2.0) and just position it in clip space instead.

[JMS55]

@IceSentry this issue can probably be closed now that we removed the old post processing example?

[IceSentry]

Yep, this isn't an issue anymore