Implement DualKawaseBlurPass

[vanruesc]

Description

Implement a DualKawaseBlurPass.

References:

• https://www.froyok.fr/blog/2021-09-ue4-custom-lens-flare/ (see section about Dual Kawase)
• https://www.shadertoy.com/view/3td3W8
• https://phabricator.kde.org/D9848

Tasks

• Create down- and upsampling shader materials.
• Create DualKawaseBlurPass.
• Add unit test.

[balraj-johal]

Hi @vanruesc, could I be assigned this issue? I'm already halfway through an implementation, I've got the down & upsampling working, and now just need to port over the Kawase shaders :)

[vanruesc]

Nice, thanks for picking this up!

[vanruesc]

@balraj-johal FYI: I've added GaussianBlurPass and updated the blur demo just now. Feel free to add the DualKawaBlurPass to that demo. The old KawaseBlurPass will be discarded.