Adaptive environment sampling on CPU and GPU

We present a production-ready approach for efficient environment light sampling which takes visibility into account. During a brief learning phase we cache visibility information in the camera space. The cache is then used to adapt the environment sampling strategy during the final rendering. Unlike existing approaches that account for visibility, our algorithm uses a small amount of memory, provides a lightweight sampling procedure that benefits even unoccluded scenes and, importantly, requires no additional artist care, such as manual setting of portals or other scene-specific adjustments. The technique is unbiased, simple to implement and integrate into a render engine. Its modest memory requirements and simplicity enable efficient CPU and GPU implementations that significantly improve the render times, especially in complex production scenes.