Foliage: Speed tree wind is reset for every add/remove/update on instances

What is happening:

  • When we invalidate the render state, proxy are recreated, causing the wind to be removed and add again, but the params are reset, causing this visual glitch.

From UE-61559
When adding new HISM instances, actors using SpeedTree -> WorldPositionOffset material are reset.

4.19 Repro project provided by user. I was unable to get WPO wind working in 4.18, I did noticed there was a change in the SpeedTree Material node from 4.18 to 4.19 (Inputs are exposed)

4.19, CL 4033788
4.20 Preview 5, CL 4173640
4.21 (UE4/Main), CL 4179794

Steps to Reproduce

4.19 Repro project attached.

1. Setup an actor with speedtree WPO material (wind)
2. Place WindDirectionalSource actor in level
3. Create a BP to add instances of wind-affected actor to level at a fixed interval.

Result: WPO (driven by wind) is reset when a new instance is added.
Expected: Individual instances WPO data is not reset.

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ComponentTools - Foliage
Affects Versions4.194.20
CreatedJul 10, 2018
UpdatedMay 31, 2019