Spectral Texturing (sketches 077) Supplementary Information

Spectral Textures are rendered by multi-layer texturing, where each layer provides a certain band of spatial frequencies for the final texture. Transparency channels introduce statistical dependencies between the layers. Figures 1 shows series of screenshots that illustrate the multilayer approach of spectral texturing. The left column shows the single texture layers, increasing in scale from top to bottom from top to bottom layers 1,2,3,4 and 5. The right columns show the results of combining the texture layers from top to bottom layers 1; 1 and 2; 1, 2 and 3; 1, 2, 3 and 4; and all five layers. There is an untextured gray plane behind the ground plane, which causes the transparent parts of the texture layers in the left column to appear grayish. All spectral textures here are rendered from high frequency towards lower frequency layers, so that it is always the lower frequencies that control the amplitudes of the higher frequencies (and not vice versa). This results in more realistic textures than if lower frequencies would be rendered first; probably because the overall amplitude spectrum of the resulting spectral texture is closer to 1/ f , as in natural images (see [Simoncelli and Olshausen 2001]). Note how the combined texture in the right column loses its repetitive features and gains complexity from top to bottom. Figure 1 shows real screenshots from an OpenGL demonstration program which have not been modified in color or contrast.The images of the main publication, on the other hand, have been slightly adapted in color and contrast to optimize print appearance.