[SOLVED] SH coordinates and Gaussian reorientation

Help & Support Gaussian Splatting
1

Hello :slight_smile:
When rotating a gaussian splatting in the editor, are the SH coordinates rotated accordingly ? or are they kept fixed and rotating my gaussian splat modify the appearance of an object if my camera has the same viewpoint relative to the object ?
Thank you

2

@slimbuck

3

Hi @boblebobbeur ,

No we don’t rotate spherical harmonics during rendering. Instead, we rotate the camera by the inverse matrix into the local space of the gaussian splat. Using this we can evaluate the spherical harmonic normally and get correct lighting.

We only ever rotate spherical harmonics in supersplat editor when a splat is exported to PLY. In this case the spherical harmonics must be rotated and applied to the data.

Does that answer your question?

Thanks!

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4

Hi thanks for the answer :),

So just to double check if I understood correctly, if I take the ply scene and rotate it by 90 degree in a given direction, what really happen is that my camera is actually rotated by 90 degree in the opposite direction (accounting for translation) ?
So if take the oxford bunny, put my camera on the tip of its nose, rotate the bunny by 90 degree and then reposition the camera on the tip of the bunny nose, the two images would be strictly identical ?
Thanks !

5

Yep :+1:t2:

1 Like
6

Cheers :smiley:

1 Like