Photon beam diffusion

摘要

An efficient numerical method for accurately rendering translucent materials using photon beam diffusion is provided that can account for multilayer materials and directional incident and exitant effects at the surface. In an embodiment, refracted incident light is represented continuously as a photon beam instead of as discrete photons. An integration scheme for calculating a radiant exitance value at a point on the surface of the translucent material is disclosed that uses importance sampling and evaluates a radiant function at a limited number of points along the beam.

主权项

1. A method of image processing, wherein a computer system processes a geometric model to generate a rendered image corresponding to a camera view of a virtual space containing the geometric model, the method comprising performing, by one or more processors of the computer system:
determining a boundary of a translucent object in the geometric model that is to be displayed in the rendered image, the translucent object having one or more parameters that define subsurface scattering properties of the translucent object; identifying an illumination source that provides one or more beams for use in generating the rendered image; for each of the one or more beams:
determining an intersection of the beam with the boundary;identifying a plurality of locations on the boundary of the translucent object;at each of the plurality of locations, determining a contribution to a radiant exitance value resulting from the beam by:
performing importance sampling to select N points along the beam according to a probability distribution function, the N points being within the translucent object, wherein each of the N points has a probability distribution function value;calculating a radiant value of a function at each of the N points, the function being dependent on the one or more parameters of the translucent object;computing a sum of the radiant values weighted by the corresponding probability distribution function values.