A method of modifying ray tracing samples after rendering and before rasterizing, comprising: obtaining a plurality of ray tracing samples from one or more passes of a ray tracing renderer that renders a three-dimensional scene, wherein each ray tracing sample of said plurality of ray tracing samples is associated with a ray in said three-dimensional scene; and each ray tracing sample of said plurality of ray tracing samples comprises a sample color; and a sample location; modifying one or more attributes of one or more ray tracing samples of said plurality of ray tracing samples to form modified ray tracing samples, after said obtaining said plurality of ray tracing samples and after said one or more passes of said ray tracing renderer; rasterizing said modified ray tracing samples into a rasterized image comprising one or more pixels of said three-dimensional scene, after said modifying one or more attributes of said one or more ray tracing samples; merging said plurality of ray tracing samples with a second set of ray tracing samples obtained from rendering of all or a portion of a second scene that is different from said three-dimensional scene, after said obtaining said plurality of ray tracing samples and after said one or more passes of said ray tracing renderer, and before said rasterizing said modified ray tracing samples into said rasterized image; selecting a quality level for a preview image; selecting a subset of said modified ray tracing samples based on said quality level; rasterizing said subset of said modified ray tracing samples into said preview image; and, displaying said preview image. obtaining a plurality of ray tracing samples from one or more passes of a ray tracing renderer that renders a three-dimensional scene, wherein each ray tracing sample of said plurality of ray tracing samples is associated with a ray in said three-dimensional scene; and each ray tracing sample of said plurality of ray tracing samples comprises a sample color; and a sample location; modifying one or more attributes of one or more ray tracing samples of said plurality of ray tracing samples to form modified ray tracing samples, after said obtaining said plurality of ray tracing samples and after said one or more passes of said ray tracing renderer; each ray tracing sample of said plurality of ray tracing samples is associated with a ray in said three-dimensional scene; and each ray tracing sample of said plurality of ray tracing samples comprises a sample color; and a sample location; a sample color; and a sample location; modifying one or more attributes of one or more ray tracing samples of said plurality of ray tracing samples to form modified ray tracing samples, after said obtaining said plurality of ray tracing samples and after said one or more passes of said ray tracing renderer; rasterizing said modified ray tracing samples into a rasterized image comprising one or more pixels of said three-dimensional scene, after said modifying one or more attributes of said one or more ray tracing samples; merging said plurality of ray tracing samples with a second set of ray tracing samples obtained from rendering of all or a portion of a second scene that is different from said three-dimensional scene, after said obtaining said plurality of ray tracing samples and after said one or more passes of said ray tracing renderer, and before said rasterizing said modified ray tracing samples into said rasterized image; selecting a quality level for a preview image; selecting a subset of said modified ray tracing samples based on said quality level; rasterizing said subset of said modified ray tracing samples into said preview image; and, displaying said preview image.