Differentiable Point-based Inverse Rendering

Hoon-Gyu Chung, Seokjun Choi, Seung-Hwan Baek
POSTECH
CVPR 2024
Paper arXiv Video Code Data

Novel view synthesis and relighting with colocated flash light.

Abstract

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.

Differentiable Forward Rendering in DPIR

Pipeline

For each 3D point, its position is used as a query for the diffuse-albedo MLP $\Theta_d$, SDF MLP $\Theta_\text{SDF}$, and specular-basis coefficient MLP $\Theta_c$. The specular-basis BRDF MLP $\Theta_s$ models specular-basis reflectance, given the incident and outgoing directions $\boldsymbol{\omega_{i}}$ and $\boldsymbol{\omega_{o}}$. The point-based shadow renderer estimates the point visibility from a light source per each image. By using the diffuse albedo, normals, specular reflectance, and visibility, we compute the radiance for each point. The radiance is then projected onto a camera plane to render the pixel color through splatting-based differentiable forward rendering.

Novel View Synthesis of Multi-view Multi-light Dataset

Relighting of Multi-view Multi-light Dataset

Reconstruction Result of Photometric Dataset

Applications

BibTeX

@inproceedings{chung2023differentiable,
  title={Differentiable Point-based Inverse Rendering},
  author={Chung, Hoon-Gyu and Choi, Seokjun and Baek, Seung-Hwan},
  booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
  year={2024}
}