T. McGraw

Tim McGraw, Asst. Professor (2005-2011)
Now at Electronic Arts : Tiburon

Contact CV Publications Students Demo Reel

Classes

	CS 470 Computer Graphics, Fall 2011 OpenGL ES and WebGL Matrices and transformations Rendering pipeline Cameras and viewing Lighting models Vertex buffer objects GL shading language : Vertex and Fragment Shaders Physics simulation Collision detection
	CS 221 Introduction to Algorithms, Fall 2011 Divide and Conquer design approach Greedy approach Searching Sorting Graph algorithms Time and space efficiency analysis
	CS 570 Advanced Computer Graphics, Spring 2011 Global illumination OpenGL 3.0+ Advanced lighting models. Tangent-space normal mapping Parallax mapping Geometry shaders Nonphotorealistic rendering High-dynamic range rendering
	CS 778/578 Medical Image Analysis, Spring 2011 Image denoising (convolution, Perona-Malik, anisotropic diffusion, TV-norm minimization, bilateral filter) Image segmentation (active contours, level-sets, region-based methods, graph cuts) Image registration (principal axes, mutual information) Image acquisition and reconstruction (CT, MRI) Visualization (scalar-, vector- and tensor-valued data)

Development Projects

	Glance : OpenGL rendering system Glance is a modular rasterization based rendering system implemented in OpenGL. The library includes methods for creating renderers which can approximate global illumination effects like diffuse inter-reflection.
	Pale : OpenGL shader development environment Pale is a visual shader editor which supports vertex, geometry and fragment shader development

Research Projects

	Mesh deformation with square-cube law compensation Geometric scaling transformations do not respect the biological processes which govern the size and shape of living creatures. In this paper we describe an approach to scaling which can be related to biological function. We use known biological laws of allometry which are expressed as power laws to control the mesh deformation in the frequency domain.
	Nonlocal mesh deformation We propose to simplifiy the mesh manipulation process by propagating editing operations from one region to other regions with similar structure.
	Visualizing High-Order Tensor Field Structure with Differential Operators Differential operators are a valuable tool for extracting features from tensor fields. A small number of these features can characterize the global field structure. Vector field operators such as gradient, divergence and curl have previously been used for visualization of flow fields. In this paper we use generalizations of these operators to locate and classify tensor field degenerate points and to partition the field into regions of homogeneous behavior.
	New scalar measures for diffusion-weighted MRI visualization (Winner of ISVC09 / iCore / MRC Best Paper Award) New scalar measures for diffusion-weighted MRI visualization are described which are based on operations of tensor calculus and have a connection to topological visualization. These operators are generalizations of the familiar divergence and curl operations in vector calculus, and apply to tensors of arbitrary order. The computation is based on a generalization of the Helmholtz decomposition.
	Variational Denoising of Diffusion-Weighted MRI A novel variational formulation for restoring high angular resolution diffusion imaging (HARDI) data is described. The restoration formulation involves smoothing signal measurements over the spherical domain and across the 3D image lattice.
	Hardware accelerated per-texel ambient occlusion mapping. By exploiting the programmable vertex and fragment processors in modern GPUs the computation of ambient occlusion maps can be greatly accelerated.
	Subdivision for tensor fields. An efficient scheme for tensor field interpolation which is inspired by subdivision surfaces in computer graphics. The method applies to Cartesian tensors of all ranks and imposes smoothness on the interpolated field by constraining the divergence and curl of the tensor field.
	Generalized Reaction-Diffusion Textures. By generalizing the equations governing anisotropic diffusion to obtain a non-Gaussian model a new reaction-diffusion process can be simulated. The resulting textures are inorganic and feature a controllable distribution of orientations, even when the diffusion process is homogeneous. A GPU implementation is described and timing results are presented.
	Stochastic DT-MRI Connectivity Mapping on the GPU. A Bayesian formulation of the fiber model is presented and it is shown that the inversion method can be used to construct plausible connectivity. An implementation of the fiber model on the graphics processing unit (GPU) is presented. Since the fiber paths can be stochastically generated independently of one another, the algorithm is highly parallelizable. This allows us to exploit the data-parallel nature of the GPU fragment processors. We also present a framework for the connectivity computation on the GPU.
	Texture-based tensor field visualization. Animation, color, intensity and texture properties such as frequency and orientation can be used to convey tensor anisotropy, mean diffusivity and principal diffusion direction.
	Von-Mises Fisher Mixture Model of the Diffusion ODF We present a novel model for representing the diffusion ODF: a mixture of von Mises-Fisher (vMF) distributions. Our model is compact in that it requires very few parameters to represent complicated ODF geometries which occur specifically in the presence of heterogeneous nerve fiber orientations. We present a Riemannian geometric framework for computing intrinsic distances (in closed-form) and for performing interpolation between ODFs represented by vMF mixtures. We also present closed-form equations for entropy and variance based anisotropy measures that are then computed and illustrated for real HARDI data from a rat brain.