From geometry to texture : experiments towards realism in computer graphics

• Main Author: Kay, Timothy L.
• Format: Others
• Published: 1992
• Online Access: https://thesis.library.caltech.edu/3028/1/Kay_tl_1992.pdf; Kay, Timothy L. (1992) From geometry to texture : experiments towards realism in computer graphics. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/XCAM-R775. https://resolver.caltech.edu/CaltechETD:etd-08062007-110815 <https://resolver.caltech.edu/CaltechETD:etd-08062007-110815>

This thesis presents a new computer graphics texture element called a texel as well as an associated rendering algorithm, which together produce an appearance never before achieved in computer graphics. Unlike previous modeling primitives, which are limited to solid, crisp appearances (e.g., metal, plastics, and glass), texels have a soft, fuzzy appearance, and thus can be used to create models and images of soft objects. This thesis presents a solution to the problem of creating fur. As an example, a Teddy bear is modeled and rendered. As part of the process, a new BDRF is developed for texels which can produce back lighting effects. A model deformation technique using trilinear solids is developed. This thesis then addresses a more complex example, that of creating a microscopic swatch of cloth by computationally "weaving" threads. The process of converting the resulting geometric model into texels is presented. The swatch of cloth is then replicated to cover the infinite plane seamlessly. A new phenomenon, the texture threshold effect is presented. It is the point at which geometry turns into texture. When viewed from beyond a certain distance threshold, the appearance of a microscopic model will converge to a macroscopic model. The position of the texture threshold is calculated. The infinite cloth model is then rendered from beyond the texture threshold, and its cloth BDRF is extracted computationally. This BDRF is then used to render a cloth-covered car seat. The BDRF extraction process involves sampling an image which contains spectral energy above the Nyquist limit. Hence, the use of point sampling in computer graphics is analyzed to verify that aliasing energy is controlled. The process of jittered subsampling is analyzed, correcting and completing previous attempts. The results confirm that it is possible to render complex computer graphics imagery avoiding artifacts from aliased energy.