My current list of publications:

1. Direct Illumination from Dynamic Area Lights
   Greg Nichols and Chris Wyman
   Poster to be presented at SIGGRAPH 2009
   Downloads: [PDF forthcoming] [DivX AVI 31MB]
2. Hierarchical Image Space Radiosity for Interactive Global Illumination
   Greg Nichols, Jeremy Shopf, and Chris Wyman
   Abstract: We introduce image-space radiosity and a hierarchical variant as a method for interactively approximating diffuse indirect illumination in fully dynamic scenes. As oft observed, diffuse indirect illumination contains mainly low-frequency details that do not require independent computations at every pixel. Prior work leverages this to reduce computation costs by clustering and caching samples in world or object space. This often involves scene preprocessing, complex data structures for caching, or wasted computations outside the view frustum. We instead propose clustering computations in image space, allowing the use of cheap hardware mipmapping and implicit quadtrees to allow coarser illumination computations. We build on a recently introduced multiresolution splatting technique combined with an image-space lightcut algorithm to intelligently choose virtual point lights for an interactive, one-bounce instant radiosity solution. Intelligently selecting point lights from our reective shadow map enables temporally coherent illumination similar to results using more than 4096 regularly-sampled VPLs.
   Accepted to the Eurographics Symposium on Rendering, June 2009
   Downloads: [Paper PDF, 3.6MB] [DivX AVI, 36MB]
3. Multiresolution Splatting for Indirect Illumination
   Greg Nichols and Chris Wyman
   
   Abstract: Global illumination provides a visual richness not achievable with the direct illumination models used by most interactive applications. To generate global effects, numerous approximations attempt to reduce global illumination costs to levels feasible in interactive contexts. One such approximation, reective shadow maps, samples a shadow map to identify secondary light sources whose contributions are splatted into eye-space. This splatting introduces significant overdraw that is usually reduced by artificially shrinking each splat's radius of inuence. This paper introduces a new, multiresolution approach for interactively splatting indirect illumination. Instead of reducing GPU fill rate by reducing splat size, we reduce fill rate by rendering splats into a multi-resolution buffer. This takes advantage of the low-frequency nature of diffuse and glossy indirect lighting, allowing rendering of indirect contributions at low resolution where lighting changes slowly and at high resolution near discontinuities. Because this multi-resolution rendering occurs on a per-splat basis, we can signicantly reduce fill rate without arbitrarily clipping splat contributions below a given threshold - those regions simply are rendered at a coarse resolution.
   Presented at the ACM Symposium on Interactive 3D Graphics and Games, February 2009
   Downloads: [Paper PDF, 10.2MB] [XviD AVI, 33.5MB]
4. Adaptive Caustic Maps Using Deferred Shading
   Chris Wyman and Greg Nichols
   
   Abstract: Caustic maps provide an interactive image-space method to render caustics, the focusing of light via reection and refraction. Unfortunately, caustic mapping suffers problems similar to shadow mapping: aliasing from poor sampling and map projection as well as temporal incoherency from frame-to-frame sampling variations. To reduce these problems, researchers have suggested methods ranging from caustic blurring to building a multiresolution caustic map. Yet these all require a xed photon sampling, precluding the use of importance-based photon densities. This paper introduces adaptive caustic maps. Instead of densely sampling photons via a rasterization pass, we adaptively emit photons using a deferred shading pass. We describe deferred rendering for refractive surfaces, which speeds rendering of refractive geometry up to 25% and with adaptive sampling speeds caustic rendering up to 200%. These benets are particularly noticable for complex geometry or using millions of photons. While developed for a GPU rasterizer, adaptive caustic map creation can be performed by any renderer that individually traces photons, e.g., a GPU ray tracer.
   Computer Graphics Forum 28(2), 309-318, April 2009
   Downloads: [Paper PDF, 2MB]
5. Exploring Volume Rendering With Path Tracing
   Scott Davis, Xiaoqian Jiang, Greg Nichols, and James Cremer
   Poster presented at SIGGRAPH 2005
   Downloads: [Abstract PDF, 78KB]
   Page last modified on June 15, 2009