**Fast Non-uniform Radiance Probe Placement and Tracing** _Symposium on Interactive 3D Graphics and Games (I3D ’19) accepted_ _Best Student Presentation_ Yue Wang^1 , Soufiane Khiat^2 , [Paul G. Kry^1](https://www.cs.mcgill.ca/~kry/), and [Derek Nowrouzezahrai^1](http://www.cim.mcgill.ca/~derek/) ^1 McGill University ^2 Ubisoft ![](./teaser_108probes_final_300dpi.png width="350px") ![](./teaser_108probes_glossy_300dpi.png width="350px") Modern Hall -- Global illumination and glossy indirect shading. Shading (17.2ms) is 20% faster and has 50% less error than regular grids [mcguire2017real], at equal probe count. -------------------------------------------------------------------------------------------------------------------------- **Abstract** Light field probes extend standard precomputed light probes to reduce light leaks and enable efficient filtered world-space ray tracing queries. When probes are placed uniformly in the scene volume, they permit an efficient querying algorithm. Manually increasing the grid resolution, however, is the only way to eliminate geometric feature undersampling, increasing the memory and computation cost of the approach. We present an automatic non-uniform probe placement method to correctly sample visibility information and eliminate superfluous probes. We organize non-uniform probes in an efficient structure for fast run-time ray tracing. Our probe placement relies on 3D scene skeletons and a gradient descent-based refinement to achieve full geometric coverage and reduce grazing angle sampling biases. Our adaptive probe ray tracer caches visibility information in a sparse voxel octree, augmenting probes with metadata used to apply a hierarchical-Z acceleration when marching rays in distant probes. We benchmark our approach on a variety of scenes and consistently demonstrate better performance, and fewer probes, in equal-quality comparisons to the state-of-the-art. **[Paper](./i3Dsubmission.pdf)** **[I3D Presentation Slides](./RadianceProbePlacement_I3D.pdf)** **[Master's Thesis](./Thesis_RadianceProbePlacement.pdf)** **[Video](https://youtu.be/jEiA3Cc8SVI)**  **BibTex** ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @inproceedings{wang2019fast, title={Fast non-uniform radiance probe placement and tracing}, author={Yue Wang and Soufiane Khiat and Paul G Kry and Derek Nowrouzezahrai}, booktitle={Proceedings of the ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games}, pages={5}, year={2019}, organization={ACM} } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~