Kai-46 / nerfplusplus

improves over nerf in 360 capture of unbounded scenes
BSD 2-Clause "Simplified" License
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What is the main point of shape-radiance ambiguity #32

Open yjhong89 opened 2 years ago

yjhong89 commented 2 years ago

Dear author,

While I read your nerf++ paper, I coudn't fully understand shape-radiance ambiguity (Section 3 of nerf++ paper).

1) Is the purpose of Figure 2 experiment illustrating the ambiguity to show that NERF model can fit to arbitrary 3d shape setting of training data ? And if it were correct (verified by Figure 2 experiment), how this fact is related to the Factor 1 ("c" must become a high-frequency function as "sigma" deviates from the correct shape) ?

2) Why the Factor 2 (NERF MLP structure implicitly regularize to make "c" have smooth BRDF prior w.r.d. "d") helps NERF to avoid the shape-radiance ambiguity ?

3) How the Factor 1 and 2 is logically related ? It seems unrelated since the Factor 1 argues NERF MLP has a limited capacity to model high complexity given incorrect shape, and the Factor 2 argues NERF MLP model implictly regularize to make "c" smooth w.r.d "d" at any given "x"

Thanks you.

Best regards, YJHong.