Alpha Invariance: On Inverse Scaling Between Distance and Volume Density in Neural Radiance Fields

arXiv:2404.02155v2 Announce Type: replace
Abstract: Scale-ambiguity in 3D scene dimensions leads to magnitude-ambiguity of volumetric densities in neural radiance fields, i.e., the densities double when scene size is halved, and vice versa. We call this property alpha invariance. For NeRFs to better maintain alpha invariance, we recommend 1) parameterizing both distance and volume densities in log space, and 2) a discretization-agnostic initialization strategy to guarantee high ray transmittance. We revisit a few popular radiance field models and find that these …

abstract alpha arxiv call cs.cv dimensions fields leads neural radiance fields property scale scaling type