Mark S. Peercy

Interactive multi-pass programmable shading

Programmable shading is a common technique for production animation, but interactive programmable shading is not yet widely available. We support interactive programmable shading on virtually any 3D graphics hardware using a scene graph library on top of OpenGL. We treat the OpenGL architecture as a general SIMD computer, and translate the high-level shading description into OpenGL rendering passes. While our system uses OpenGL, the techniques described are applicable to any retained mode interface with appropriate extension mechanisms and hardware API with provisions for recirculating data through the graphics pipeline. We present two demonstrations of the method. The first is a constrained shading language that runs on graphics hardware supporting OpenGL 1.2 with a subset of the ARB imaging extensions. We remove the shading language constraints by minimally extending OpenGL. The key extensions are color range (supporting extended range and precision data types) and pixel texture (using framebuffer values as indices into texture maps). Our second demonstration is a renderer supporting the RenderMan Interface and RenderMan Shading Language on a software implementation of this extended OpenGL. For both languages, our compiler technology can take advantage of extensions and performance characteristics unique to any particular graphics hardware.

Efficient bump mapping hardware

We present a bump mapping method that requires minimal hardware beyond that necessary for Phong shading. We eliminate the costly per-pixel steps of reconstructing a tangent space and perturbing the interpolated normal vector by a) interpolating vectors that have been transformed into tangent space at polygon vertices and b) storing a precomputed, perturbed normal map as a texture. This represents a considerable savings in hardware or rendering speed compared to a straightforward implementation of bump mapping. CR categories and subject descriptors: I.3.3 [Computer Graphics]: Picture/Image generation; I.3.7 [Image Processing]: Enhancement

A performance-oriented data parallel virtual machine for GPUs

Existing GPU programming interfaces require applications to adopt a graphics-centric programming model exported by a device driver tuned for real-time graphics and games. This programming model, however, hinders the development and performance of non-graphics applications by imposing a graphics policy for program execution and hiding hardware resources. We present a new virtual machine abstraction for GPUs that provides policy-free, low-level access to the hardware and is designed for high-performance, data-parallel applications.

Linear color representations for full speed spectral rendering

We present a general linear transform method for handling full spectral information in computer graphics rendering. In this framework, any spectral power distribution in a scene is described with respect to a set of fixed orthonormal basis functions. The lighting computations follow simply from this decision, and they can be viewed as a generalization of point sampling. Because any basis functions can be chosen, they can be tailored to the scenes that are to be rendered. We discuss efficient point sampling for scenes with smoothly varying spectra, and we present the use of characteristic vector analysis to select sets of basis functions that deal efficiently with irregular spectral power distributions. As an example of this latter method, we render a scene illuminated with fluorescent light.