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Next: 1.35 Diagnostic modes Up: 1. Functionality Previous: 1.33 Volume Caustics

# 1.34 Global Illumination in Participating Media

Global illumination in volumes can be used to simulate indirect light interactions in volumic media, such as:

- color bleeding from a colored wall onto gray smoke.

- multiple light scattering in clouds or other participating media, such as the glow around the beam from a car headlight in fog.

Global illumination in participating media is computed much the same way as global illumination on surfaces, except that volume shaders and volume photon shaders are needed.

To change the number of photons used to compute the local intensity of global illumination in volumes, specify a `photonvol accuracy` (and optionally a radius) in the `options` (similar to volume caustics).