Unexpected color shifting tint in latest Supersplat (1.11.2)

[tonetechnician]

Hi there,

I've been picking up a color shift from blue to red in the latest supersplat that I didn't pick up in previous versions i.e (1.9.0).

I've attached an example splat to test with.

test.zip

Not quite sure what could be causing it, but seems consistent but thought I'd report it.

[slimbuck]

Hi @tonetechnician,

Well first of all it must be said that this happens to be one of the coolest cars ever, well done.

I managed to repro the color tint. It looks like perhaps spherical harmonics related.

Thanks so much for reporting this and providing a repro - I will investigate immediately.

Thanks!

[slimbuck]

I found the issue with the coloring (see here) for details, but also noticed that this model does not compress to compressed.ply format correctly. I've never seen this before and will investigate next.

[tonetechnician]

Epic! Thanks @slimbuck

Haha, glad you appreciate that car ;)

And I agree, when disabling SH bands I see the issue goes away - thanks for the speedy fix! Hmmm, the compression could be related to me as we are using a homerolled ply exporter. Will also have a look as compression is something we do want!

[slimbuck]

This ticket is closed, but the fix will be deployed after the next engine release. I may push this fix through quickly, so early next week.

Regarding the compressed.ply export going wrong, it looks like the scene's quaternions are being badly exported. Still investigating.

[slimbuck]

Ah ok, scale_2 for most splats is -Infinity and we're not handling that correctly during compression (though we obviously render it fine).

My guess is this scene was trained with some sort of 2dgs?

Anyway, I'll also get this fixed on our side.

[tonetechnician]

Hey @slimbuck

Ah, ok, that would makes sense! Indeed, this is trained with 2DGS, which would explain that case. Should've specified this earlier.

[vincentwoo]

@tonetechnician this is offtopic, but I didn't realize you could render 2dgs output in supersplat- do you have any notes anywhere about (a) how you trained your 2dgs splat and (b) if you need to do anything special to get it compatible with supersplat?

[slimbuck]

Hi @vincentwoo ,

SuperSplat will add scale_2 at load time if it's missing (2dgs), but it doesn't then remove it on save. I think we have a ticket open for this.

It means 2dgs roughly works in SuperSplat, but just treats the gaussians as very thin 3dgs.

Thanks

[vincentwoo]

thanks!

[slimbuck]

Please open an issue if there's anything specific you'd like for Supersplat to support 2dgs better. Or even better submit a pr with changes yourself 😛.

[tonetechnician]

@tonetechnician this is offtopic, but I didn't realize you could render 2dgs output in supersplat- do you have any notes anywhere about (a) how you trained your 2dgs splat and (b) if you need to do anything special to get it compatible with supersplat?

Hey @vincentwoo

This is pretty standard in the nerfstudio gsplat repo.

To train I use --> https://github.com/nerfstudio-project/gsplat/blob/main/examples/simple_trainer_2dgs.py

You can use this with colmap format or write your own parser for the data you are working with.

Then the only thing extra needed is the ability to save ply which you can get from nerfstudio's project

https://github.com/nerfstudio-project/nerfstudio/blob/main/nerfstudio/scripts/exporter.py#L490C7-L490C26

Hope this helps!