Certain GPU drivers do not handle shader branching correctly

[brianchirls]

Originally reported here: processing/p5.js-video#40

This is tricky to replicate, as it seems to be a problem only for certain devices. It first manifested as complete lack of any alpha channel on images processed by the Chroma effect. Testing with a split effect showed that the same users were seeing white dots along the edge where the shader had branching. A version of the shader without branching solved the problem.

This ticket is to remove branching from effects wherever possible, starting with Split and Chroma.

[brianchirls]

@Xeronimo74 Would you care to take the examples for a spin and to see if any of the other effects aren't working?

http://brianchirls.github.io/Seriously.js/examples/

[GanWeaving]

@brianchirls
animationwith seriously.go has the white dot problem (Chrome, Win7)

the others all seem to work fine (couldn't test those who required a camera)

[brianchirls]

Thanks for testing. That's good news.

The examples are based on the master branch, so the new version of the split effect is not in there yet. There are several other effects that have branching in the shaders (e.g. blend, accumulator, channels, displacement, etc.) but for some reason, they don't seem to be a problem for you. So I'm gonna close this one for now, and we'll keep an eye on the issue.

@scottgarner has been notified of the updated Chroma effect, and he can add it to the p5js site when he's ready. Both Chroma and Split will be updated with the next release of Seriously.js.