プロメテックCGリサーチの論文が「SIGGRAPH 2025」のTechnical Papers部門に採択　～ EUROGRAPHICS 2025でも連続採択を達成 ～

論文タイトル

“ Spherical Lighting with Spherical Harmonics Hessian ”

著者（所属）

岩崎 慶（埼玉大学・プロメテックCGリサーチ）、
土橋宜典（北海道大学・プロメテックCGリサーチ）

概要

In this paper, we introduce a second-order derivative of spherical harmonics, spherical harmonics Hessian, and solid spherical harmonics, a variant of spherical harmonics, to the computer graphics community. These mathematical tools are used to develop an analytical representation of the Hessian matrix of spherical harmonics coefficients for spherical lights. We apply our analytic representation of the Hessian matrix to grid-based SH lighting rendering applications with many spherical lights that store the incident light field as spherical harmonics coefficients and their spatial gradient at sparse grid. We develop a Hessian-based error metric, with which our method automatically and adaptively subdivides the grid whether the interpolation using the spatial gradient is appropriate. Our method can be easily incorporated into the grid-based precomputed radiance transfer (PRT) framework with small additional storage. We demonstrate that our adaptive grid subdivided by using the Hessian-based error metric can substantially improve the rendering quality in equal-time grid construction.

論文タイトル

“ Importance Sampling of BCSDF Derivatives ”

著者（所属）

Lei Wang（埼玉大学）、
岩崎 慶（埼玉大学・プロメテックCGリサーチ）

概要

Differentiable rendering requires the development of importance sampling for derivative functions with respect to the parameters. While importance sampling for Bidirectional Reflectance Distribution Function derivative has been proposed in recent years, no methods have been introduced for the derivatives of Bidirectional Curve Scattering Distribution Function (BCSDF). To bridge this gap, we propose an importance sampling method for the derivatives of the BCSDF using positivization [BXB∗24]. Our BCSDF derivative importance sampling method achieves up to 94% reduction in RMSE for eqaul-time rendering.