Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for image rendering. One of the methods includes receiving data describing a scene, wherein the scene comprises one or more light sources and one or more objects having different surface optical properties; receiving a request to render an image of the scene using a multiple importance sampling method that combines a plurality of sampling techniques, wherein each sampling technique uses a different probability distribution to sample a respective fraction of total number of samples; modifying a particular one of the probability distributions to reduce a variance of the multiple importance sampling while holding the respective fractions and the other probability distributions fixed; rendering the scene using the multiple importance sampling using the modified particular probability distribution and the other probability distributions; and outputting the rendered scene in response to the request.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for image rendering. One of the methods includes receiving data describing a scene, wherein the scene comprises one or more light sources and one or more objects having different surface optical properties; receiving a request to render an image of the scene using a multiple importance sampling method that combines a plurality of sampling techniques, wherein each sampling technique uses a different probability distribution to sample a respective fraction of total number of samples; modifying a particular one of the probability distributions to reduce a variance of the multiple importance sampling while holding the respective fractions and the other probability distributions fixed; rendering the scene using the multiple importance sampling using the modified particular probability distribution and the other probability distributions; and outputting the rendered scene in response to the request.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for rendering an image of a scene affected by multiple light sources. In one aspect, a method includes subdividing the scene into cells; sampling light source —point pairs; for each pair, determining a contribution value of the light source to the point; for each cell and each light source: determining a maximum contribution value of the contribution values for the light source to the color of the points that are in the cell, and determining, based on the maximum contribution value, a significance value that is a measure of an estimated importance of the light source in rendering a portion of the image corresponding to the cell; and rendering the image of the scene by sampling light sources having a higher significance value more often than light sources having a lower significance value.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for rendering an image of a scene affected by multiple light sources. In one aspect, a method includes subdividing the scene into cells; sampling light source—point pairs; for each pair, determining a contribution value of the light source to the point; for each cell and each light source: determining a maximum contribution value of the contribution values for the light source to the color of the points that are in the cell, and determining, based on the maximum contribution value, a significance value that is a measure of an estimated importance of the light source in rendering a portion of the image corresponding to the cell; and rendering the image of the scene by sampling light sources having a higher significance value more often than light sources having a lower significance value.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for rendering an image. One of the methods includes, for each of a plurality of pixels of the image: maintaining current color data for each of a plurality of render elements generated by sampling color contribution values for the render element for the pixel; determining, for each of the plurality of render elements, whether or not to sample another color contribution value for the render element from the current color data for the render element for the pixel and the current color data for the render element for one or more pixels that neighbor the pixel in the image; and sampling a new color contribution value only for the render elements for which it was determined to sample another contribution value.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for rendering an image. One of the methods includes, for each of a plurality of pixels of the image: maintaining current color data for each of a plurality of render elements generated by sampling color contribution values for the render element for the pixel; determining, for each of the plurality of render elements, whether or not to sample another color contribution value for the render element from the current color data for the render element for the pixel and the current color data for the render element for one or more pixels that neighbor the pixel in the image; and sampling a new color contribution value only for the render elements for which it was determined to sample another contribution value.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for shading computer graphics (CG) representations of materials. One of the methods includes obtaining data describing a physical material; receiving a shading request to shade a particular point in a CG representation of the physical material from a rendering engine, wherein the request identifies a mapping position of the particular point, a view direction at the mapping position, and a light direction at the mapping position; calculating a direct lighting color at the mapping position using a plurality of palletized images; calculating an indirect lighting color at the mapping position using the data describing the physical material; generating a final color at the mapping position by combining the direct lighting color and the indirect lighting color; and providing the final color to the rendering engine for use in rendering the CG representation of the physical material.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for shading computer graphics (CG) representations of materials. One of the methods includes obtaining data describing a physical material; receiving a shading request to shade a particular point in a CG representation of the physical material from a rendering engine, wherein the request identifies a mapping position of the particular point, a view direction at the mapping position, and a light direction at the mapping position; calculating a direct lighting color at the mapping position using a plurality of palettized images; calculating an indirect lighting color at the mapping position using the data describing the physical material; generating a final color at the mapping position by combining the direct lighting color and the indirect lighting color; and providing the final color to the rendering engine for use in rendering the CG representation of the physical material.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for shading computer graphics (CG) representations of materials. One of the methods includes obtaining data describing a physical material; receiving a shading request to shade a particular point in a CG representation of the physical material from a rendering engine, wherein the request identifies a mapping position of the particular point, a view direction at the mapping position, and a light direction at the mapping position; calculating a direct lighting color at the mapping position using a plurality of palettized images; calculating an indirect lighting color at the mapping position using the data describing the physical material; generating a final color at the mapping position by combining the direct lighting color and the indirect lighting color; and providing the final color to the rendering engine for use in rendering the CG representation of the physical material.