Transform behavior does not match supersplat editor

[vincentwoo]

I transformed a splat with the same parameters I tweaked in supersplat:

but the result came out upside down after running the same splat through splat-transform interior_seeded_hog_3m.ply -t '0,0.71,0' -r '93.19,5.11,-179.27' test.ply

Is this working as intended?

[slimbuck]

Yeah this is a bit confusing.

Supersplat editor by default sets PLY transform to (0, 0, 180) in order to match the playcanvas engine coordinate system while editing models.

When the editor then saves back to PLY it applies a (0, 0, -180) rotation (otherwise the PLY would be flipped upside-down). If you don't change the transform during editing in SuperSplat the two transforms (0, 0, 180) and (0, 0, -180) would cancel each other out.

So in order to match the transform in Supersplat editor transform panel, you must include the extra (0, 0, -180) rotation. In your case I think you can just make z rotation 0.73.

This is definitely a bit confusing, but I'm not entirely sure how to solve it RN.

[vincentwoo]

Does supersplat perform position, rotation, scale transformations in that order? I'm realizing splat-transform order of operations matters too.

[slimbuck]

We use the engine function setTRS which mathematically is written as M = T * R * S, but results in a matrix which first scales the vertex, then rotates it, then translates it.