  We present differentiable point-based inverse rendering, DPIR, an
analysis-by-synthesis method that processes images captured under diverse
illuminations to estimate shape and spatially-varying BRDF. To this end, we
adopt point-based rendering, eliminating the need for multiple samplings per
ray, typical of volumetric rendering, thus significantly enhancing the speed of
inverse rendering. To realize this idea, we devise a hybrid point-volumetric
representation for geometry and a regularized basis-BRDF representation for
reflectance. The hybrid geometric representation enables fast rendering through
point-based splatting while retaining the geometric details and stability
inherent to SDF-based representations. The regularized basis-BRDF mitigates the
ill-posedness of inverse rendering stemming from limited light-view angular
samples. We also propose an efficient shadow detection method using point-based
shadow map rendering. Our extensive evaluations demonstrate that DPIR
outperforms prior works in terms of reconstruction accuracy, computational
efficiency, and memory footprint. Furthermore, our explicit point-based
representation and rendering enables intuitive geometry and reflectance
editing.
