Motion blur is sometimes broken

[illwieckz]

I forgot to create an issue for that but I mentioned there before:

• motionblur: Disable by default Unvanquished/Unvanquished#3093

Motion blur is broken

[illwieckz]

I dislike to now know how I reproduced it, but I don't reproduce it anymore.

[VReaperV]

Apparently @sweet235 got the same issue recently:

So the bug is still there.

[illwieckz]

I bet it's not a blur bug but a GLSL shader cache bug. Let's re-open it if we reproduce it later after having no one doubt on the GLSL shade cache.

[VReaperV]

Did we have any changes to the blur/contrast shaders at the time?

[slipher]

Motion blur uses the depth texture, so this may be related to the texture feedback issues like #1616. We've added some texture barriers now, though AMD + Mesa continues to have some problems.

[slipher]

#1816 will add a texture barrier especially for motion blur.