Backwards rendering / invert raasterization process

[EarltShirt]

Hello, thanks for your excellent work !

I'm currently working on some additions to the 3DGS repo, namely integrating the segment anything module. In order to proceed I need some help / answers :

I wanted to know if it is possible to invert the rasterization process / back trace the gaussians, meaning I would like to retrieve all the gaussians that are contributing to the color of a pixel or set of pixels on the screen. I know it can be done using the radii, centers and the transformation matrix associated to the view, but wanted to assure myself that something similar wasn't already available inside your repo.

In my case, I have multiple 2D masks of the same object and try to generate the associated 3D mask by seeing which gaussians contribute to the pixels contained in the 2D masks.

Thanks a lot for your time and help !