We introduce a new class of primitive functions with non-linear parameters for representing light reflectance functions. The functions are reciprocal, energy-conserving and expressive. They can capture important phenomena such as off-specular reflection, increasing reflectance and retro-reflection. We demonstrate this by fitting sums of primitive functions to a physically-based model and to actual measurements. The resulting representation is simple, compact and uniform. It can be applied efficiently in analytical and Monte Carlo computations.
Our goal is to develop physically based lighting models and perceptually based rendering procedures for computer graphics that will produce synthetic images that are visually and measurably indistinguishable from real-world images. Fidelity of the physical simulation is of primary concern. Our research framework is subdivided into three sub-sections: the local light reflection model, the energy transport simulation, and the visual display algorithms. The first two subsections are physically based, and the last is perceptually based.We emphasize the comparisons between simulations and actual measurements, the difficulties encountered, and the need to utilize the vast amount of psychophysical research already conducted. Future research directions are enumerated. We hope that results of this research will help establish a more fundamental, scientific approach for future rendering algorithms. This presentation describes a chronology of past research in global illumination and how parts of our new system are currently being developed. But are these images correct? Would they accurately represent the scene if the environment actually existed? In general, the answer is no; yet the results are appealing because the resulting images are believable. CR Categories and
We describe an automated three-axis BRDF measurement instrument that can help increase the physical realism of computer graphics images by providing light scattering data for the surfaces within a synthetic scene that is to be rendered. To our knowledge, the instrument is unique in combining wide angular coverage (beyond 85° from the surface normal), dense sampling of the visible wavelength spectrum (1024 samples), and rapid operation (less than ten hours for complete measurement of an isotropic sample). The gonioreflectometer employs a broadband light source and a detector with a diffraction grating and linear diode array. Validation was achieved by comparisons against reference surfaces and other instruments. The accuracy and spectral and angular ranges of the BRDFs are appropriate for computer graphics imagery, while reciprocity and energy conservation are preserved. Measured BRDFs on rough aluminum, metallic silver automotive paint, and a glossy yellow paint are reported, and an example rendered automotive image is included.
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