[10.x.x] Add SpeedTree8 shadergraph to HDRP and URP (#3861)

* Squashed commits for 19.4's ST8 support

* Add wind enable/disable toggle to HD ST8 shader.

* Fixup URP SpeedTree8 shader. Hookup GI for both ST8 shaders.

* Update HD ST8 test scene to test various wind qualities and wind enable
toggle.

* Fix double-sided setting on billboard materials.

* Remove redundant keyword enable per review.

* Remove unused keyword from HD ST8

* Updated changelogs for SpeedTree8 addition.

* Add ST8 shadergraphs to HD and Universal, including supporting
subshadergraphs in ShaderGraph and MaterialUpgrader in core. Add a test
to HDRP for speedtree8.

* Fixup SpeedTree8 test rename

* Add reference images for linuxeditor/vulkan

* Fixup LOD0 material misassignment

* Clean up renamed HDLitGUI

* Update reference images from first 10.x.x yamato runs. (Darker shadows)

* Merge hue variation, crossfade, and seam blending into
SpeedTree8ColorAlpha subgraph. Fix Base Map naming in URP ST8
shadergraph. Fix wait framerate in HD ST8 test.

* Modify hue variation subgraph to match handwritten ST8 shader

* Add lerp hue variation behavior for backwards compatibility. Only expose
this property in universal ST8.

* Format files that need it

* Update reference images after fixing frame wait time for HD ST8 test

* Hook up GI and subsurface scattering in handwritten SpeedTree8 Universal
shader

* Update test materials to use a diffusion profile. Set thickness to 100
when subsurface is disabled.

* Grab default foliage diffusion profile when importing or upgrading an HD ST8
shader

* Remove subsurface enable from ST8 shader. Update ST8 test scene to use
foliage diffusion profile.

* Remove wait time from HD ST8 test

* Modulate subsurface with _SubsurfaceIndirect property

* Fix SpeedTree8 subsurface per feedback

* Update reference images for HD ST8 test after changing to foliage diffusion profile and
disabling wind

* Update SpeedTree8 shader to sample shadowmap when attenuating direct
subsurface. Update ST8 shadergraph to match subsurface calculations.

* Update shadergraph changelog after refactoring subshadergraphs for ST8.
Move LODCrossfade.hlsl out of Nature-specific folder.

* Fix hue variation randomization to work with HD's camera relative
rendering

* Change default Subsurface color to black from white

* Fix URP shadergraph default subsurface color and texture

* Update HDRP reference images once more- trunks are a slightly different
color?

* Update failing tests after handwritten ST8 shader was updated.

* Set alpha to 0 on billboard backfaces

* Update HD ST8 shadergraph after billboard subshadergraph was modified

* Normalize view direction when calculating subsurface

* Convert floats to sliders. Add a Diffusion profile property so that it
can be grouped with subsurface properties.

* Incorporate docs feedback

* Fix HD ST8 test material diffusion profiles after diffusion profile
property change

* Docs feedback on changelogs

* Clean up redundant GGX code in SpeedTree8Passes. Add comment to
LODCrossfade explaining its redundancy with existing Common.hlsl code.

* Renamed LODCrossfade to make clear its relation to the core
LODDitheringTransition function.

* Docs changes.

* Test universal iphone failure

* Docs changes

* Only generate camera motion vectors when importing ST8 asset to SRP.

* Clean up ST8 shader warnings where possible

* Update HD ST8 ref images after adding an abs() to subsurface calculation

* Update HDRP Metal reference screenshots 1601_TerrainLit

* Revert "Update HDRP Metal reference screenshots 1601_TerrainLit"

This reverts commit 39dfb3c.

Co-authored-by: Tianliang Ning <[email protected]>
Co-authored-by: Sebastien Lagarde <[email protected]>

Author: 3 people