Questions about f_rest property in .ply file

[NithinJangid]

Hello, I appreciate your excellent work. I have a few questions that I’d like to understand better. Could you please explain?

Q1) Could you please provide a detailed explanation of the f_rest property in the context of Gaussian Splatting? Q2) Is it possible to generate or render an image without the f_rest property, and if so, will the quality of the image be affected? Q3) I’ve noticed that some Gaussian Splatting repositories do not include the f_rest property in their PLY files. Could you explain why this is the case? Q4) The paper mentions that at “30K iterations reaches about 200–500K Gaussians per scene”. Is there a method to cap the number of Gaussians to a specific limit, such as 150k or 200K? Q5) Is there a strategy to accelerate the training process without compromising the Image resolution and render quality?

[zhumorui]

f_rest are parameters of spherical harmonics to storage the colors. If you set sh_degree=0 while trainig 3D GS, it won't generate f_rest parameters. But I think there is a bug to render 3D GS in SIBR_viewer with sh_degree=0. However, you can use many other viewers to visualize it, e.g. https://github.com/mkkellogg/GaussianSplats3D.

[lxzbg]

SIBR_viewer is hard-coded in SH and can only work under sh_degree=2. You can modify the source code or use other viewers, as @zhumorui said.