# Fast Global Illumination Approximations on Deep G-Buffers Michael Mara, Morgan McGuire, Derek Nowrouzezahrai, David Luebke · 2014 [file](https://files.dgkn.uk/papers/2014-mara-fast-global-illumination-approximations-on-deep.pdf) ## Abstract Deep Geometry Buffers (G-buffers) combine the fine-scale and efficiency of screen-space data with much of the robustness of voxels. We introduce a new hardware-aware method for computing two-layer deep G-buffers and show how to produce dynamic indirect radiosity, ambient occlusion (AO), and mirror reflection from them in real-time. Our illumination computation approaches the performance of today’s screen-space AO-only rendering passes on current GPUs and far exceeds their quality. Our G-buffer generation method is order-independent, guarantees a minimum separation between layers, operates in a (small) bounded memory footprint, and avoids any sorting. Moreover, to address the increasingly expensive cost of pre-rasterization computations, our approach requires only a single pass over the scene geometry. We show how to apply Monte Carlo sampling and reconstruction to these to efficiently compute global illumination terms from the deep G-buffers. ## My notes two layer g buffer, rendered in single pass (reprojection from velocity, delay or latency), regular methods just optimized and adjusted them with different parameters, novel idea is 2 layer depth with 50cm gap between them