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PxrUPBP fully supports multiple scattering of homogeneous volumes, including multiple overlapping homogeneous volumes and anisotropic scattering. Bidirectional path tracing, in particular, is well suited for multiple scattering in volumes. PxrUPBP improves performance by supporting a combination of volumetric photon points and beams, giving less noise in direct volume illumination and especially indirect volume illumination such as volume caustics. Inhomogeneous volumes are not yet supported.

There is an important difference to note between this integrator and PxrVCM:

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