I am having very similar issues — here is a breakdown of the current state of things – all in version 8.3.1 (also the same in 8.2)
These are all the same model in different formats. Created in postshot, exported as a ply.
1 - Compressed PLY does not seem to be functional at all, this is a ply file from postshot converted to a compressed ply in supersplat - https://playground.babylonjs.com/#KUHXDT#13
2 - .SPZ looks great and the harmonics are correct when using webGL only - https://playground.babylonjs.com/#KUHXDT#8. webGPU is all broken looking - https://playground.babylonjs.com/#KUHXDT#7
3 - PLY is broken in the latest version - it looks bad and it is inverted from the way it was in prior versions. Seems like we are trying to bring sphereical harmonics support to plys (great!) -
v8.3 - https://playground.babylonjs.com/#KUHXDT#14
v7.54 - https://playground.babylonjs.com/#KUHXDT#15
The new orientation for ply seems to match the orientation of .spz files - while the old version of ply without harmonics has the same orientation as .splat files.
4 - .splat files look fine and the same as they did before -https://playground.babylonjs.com/#KUHXDT#16
The new orientation is coming into the scene by default inverted, which is fine since we can fix that by inverting scale, but it would be great to be able to unify this behavior across all file types, harmonics or not and have them always face up.
@Cedric I know you are off so take your time, I just wanted to get all of my thoughts down in one place and give this info to you ASAP. I will continue to update this thread if I find any new info and put it in an update below.
Here is another thread I started on this issue - Bug with WebGPU rendering some .SPZ files - #2 by Evgeni_Popov