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Figure 1: We present a new approach to compute scattering parameters at reduced resolutions. Many detailed appearance models involve high-resolution volumetric representations (top-left). Such level of detail leads to high storage but is usually unnecessary especially when the object is rendered at a distance. However, naïve downsampling often loses intrinsic shadowing structures and brightens resulting images (see the insets). Our method computes scaled phase functions, a combined representation of single-scattering albedo and phase function, and provides significantly better accuracy while reducing the data size by almost three orders of magnitude (top-right).
AbstractVolumetric micro-appearance models have provided remarkably high-quality renderings, but are highly data intensive and usually require tens of gigabytes in storage. When an object is viewed from a distance, the highest level of detail offered by these models is usually unnecessary, but traditional linear downsampling weakens the object's intrinsic shadowing structures and can yield poor accuracy. We introduce a joint optimization of single-scattering albedos and phase functions to accurately downsample heterogeneous and anisotropic media. Our method is built upon scaled phase functions, a new representation combining abledos and (standard) phase functions. We also show that modularity can be exploited to greatly reduce the amortized optimization overhead by allowing multiple synthesized models to share one set of downsampled parameters. Our optimized parameters generalize well to novel lighting and viewing configurations, and the resulting data sets offer several orders of magnitude storage savings.