This is a port of the previous implementation but using compute
shaders instead of using the raster pipeline for every steps.
Only the scatter passes is kept as a raster pass for obvious performance
reasons.
Many steps have been rewritten to take advantage of LDS which allows faster
and simpler downsampling and filtering for some passes.
A new stabilize phase has been separated from another setup pass in order
to improve it in the future with better stabilization.
The scatter pass shaders and pipeline also changed. We now use indirect
drawcall to draw quads using triangle strips primitives. This reduces
fragment shader invocation count & overdraw compared to a bounding
triangle. This also reduces the amount of vertex shader invocation
drastically to the bare minimum instead of having always 3 verts per
4 pixels (for each ground).
The improvements over the old implementation are:
- Improved history reprojection filter (catmull-rom)
- Use proper velocity for history reprojection.
- History clipping is now done in YCoCg color space using better algorithm.
- Velocity is dilated to keep correct edge anti-aliasing on moving objects.
As a result, the 3x3 blocks that made the image smoother in the previous
implementation are no longer visible is replaced by correct antialiasing.
This removes the velocity resolve pass in order to reduce the bandwidth
usage. The velocities are just resolved as they are loadded in the film
pass.
This modules handles renderpasses allocation and filling. Also handles
blitting to viewport framebuffer and render result reading.
Changes against the old implementation:
- the filling of the renderpasses happens all at once requiring
only 1 geometry pass.
- The filtering is optimized with weights precomputed on CPU and
reuse of neighboor pixels.
- Only one accumulation buffer for renderpasses (no ping-pong).
- Accumulation happens in one pass for every passes using a single
dispatch or fullscreen triangle pass.
TAA and history reprojection is not yet implemented.
AOVs support is present but with a 16 AOV limit for now.
Cryptomatte is not yet implemented.
