About var spp

[wkMvg]

Hi,
instant ngp is really a great work;
I have question about var spp; what does it mean? samples per pixel? If traditional nerf, samples per ray is about 64 or 128; I read run.py that you set it as 8; So I am confused about it. Can you explain it? Thx a lot

[Tom94]

Hi there, spp indeed refers to "samples per pixel", but a "sample" on the image plane is an entire ray. So spp=8 effectively means that the rendered images have 8x super-sampled anti aliasing, where each of the 8 rays per pixel uses a raymarching step size according to the description in the paper. It's a bit more complicated than taking a fixed number of steps (as original NeRF would): empty space is skipped and occluded regions are culled away.

[wkMvg]

Got it! Thx!