Adaptive importance photon shooting technique

• Our technique accelerates the convergence rate of the photon mapping by adaptively shooting photons.
• The photons in the scene are organized by kd-tree and used to compute the feature error.
• The feature error is used to build an adaptive cumulative distribution function.
• The cumulative distribution function redirects the photon's reflection direction during its tracing path.
• Our technique can be used in progressive photon mapping with bounded memory consumption.

Photon mapping is an efficient technique in global illumination and participating media rendering, but it converges slowly in complex scenes. We propose an adaptive importance photon shooting technique to accelerate the convergence rate. We analyze the scene space and build cumulative distribution functions on the surfaces to adaptively shoot photons. The rendering space is partitioned by kd-tree structure. The photons tracing through the scene are stored in the kd-tree node. An error criterion is proposed to estimate the feature error of the local light field in each node. In order to adaptively shoot photons, a novel adaptive cumulative distribution function is built in each node based on their neighbors' error values. When a photon hits a surface in the scene, the reflection direction of this photon is adaptively chosen by our cumulative distribution function. Our technique can be used in both photon mapping and progressive photon mapping. The experiments show that our adaptive importance photon shooting technique gives better results than the previous methods in both visual quality and numerical error.

We propose a technique to adaptively shoot photons. The feature error in the scene is used to build the cumulative distribution function. The cumulative distribution function guides the photons during their tracing path.Figure optionsDownload high-quality image (207 K)Download as PowerPoint slide