Holger Dammertz, Johannes Hanika

We present a method to start light paths on an emitting environment map
in the context of Monte Carlo global illumination with image-based lighting or physical sky models. With this technique, we can efficiently render unbiased caustics from these kinds of lights, for example using bi-directional path tracing. Additionally, it is now possible to use algorithms like multiple importance sampling, photon mapping, and instant radiosity correctly with environment maps.

Holger Dammertz and Johannes Hanika, in journal of graphics, gpu, and game tools, volume 14, number 2, pp 25-31, 2009.

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