This website is a portfolio of my research and publications, plus access to my resume and a few other things. I am currently a PhD student in Computer Science (Computer Graphics) at the University of British Columbia. My supervisor is Dr. Wolfgang Heidrich.

Image-Based 3D Reconstruction

	Synchronization and Rolling Shutter Compensation for Consumer Video Camera Arrays       PDF        D. Bradley, B. Atcheson, I. Ihrke, W. Heidrich. Proceedings of International Workshop on Projector-Camera Systems (PROCAMS). 2009. (Miami, USA). Two major obstacles to the use of consumer camcorders in computer vision applications are the lack of synchronization hardware, and the use of a "rolling" shutter, which introduces a temporal shear in the video volume. We present two simple approaches for solving both the rolling shutter shear and the synchronization problem at the same time. The first approach is based on strobe illumination, while the second employs a subframe warp along optical flow vectors. In our experiments we have used the proposed methods to effectively remove temporal shear, and synchronize up to 16 consumer-grade camcorders in multiple geometric configurations
	Wrinkling Captured Garments Using Space-Time Data-Driven Deformation       PDF    AVI T. Popa, Q. Zhou, D. Bradley, V. Kraevoy, H. Fu, A. Sheffer, W. Heidrich. Proceedings of Eurographics. 2009. (Munich, Germany). In this work we propose a method for reintroducing fine folds into captured garment models using data- driven dynamic wrinkling. We first estimate the shape and position of folds based on the original video footage used for capture and then wrinkle the surface based on those estimates using space-time deformation. Both steps utilize the unique geometric characteristics of garments in general, and garment folds specifically, to facilitate the modeling of believable folds. We demonstrate the effectiveness of our wrinkling method on a variety of garments that have been captured using several recent techniques.
	Time-resolved 3D Capture of Non-stationary Gas Flows       PDF    AVI B. Atcheson, I. Ihrke, W. Heidrich, A. Tevs, D. Bradley, M. Magnor, H.-P. Seidel. ACM Transactions on Graphics (Proceedings of SIGGRAPH Asia). 2008. (Singapore). Fluid simulation is one of the most active research areas in computer graphics. However, it remains difficult to obtain measurements of real fluid flows for validation of the simulated data. In this paper, we take a step in the direction of capturing flow data for such purposes. Specifically, we present the first time-resolved Schlieren tomography system for capturing full 3D, non-stationary gas flows on a dense volumetric grid.
	Markerless Garment Capture       PDF    AVI D. Bradley, T. Popa, A. Sheffer, W. Heidrich, T. Boubekeur. ACM Transactions on Graphics (Proceedings of SIGGRAPH). 2008. (Los Angeles, USA). In this paper, we describe a marker-free approach to capturing garment motion. We establish temporally coherent parameterizations between incomplete geometries that we extract at each timestep with a multiview stereo algorithm. We then fill holes in the geometry using a template. This approach, for the first time, allows us to capture the geometry and motion of unpatterned, off-the-shelf garments made from a range of different fabrics.
	Accurate Multi-View Reconstruction Using Robust Binocular Stereo and Surface Meshing       PDF D. Bradley, T. Boubekeur, W. Heidrich. IEEE Computer Vision and Pattern Recognition (CVPR) 2008. (Anchorage, USA). This paper presents a new algorithm for multi-view reconstruction that demonstrates both accuracy and efficiency. Our method is based on robust binocular stereo matching, followed by adaptive point-based filtering of the merged point clouds, and efficient, high-quality mesh generation. All aspects of our method are designed to be highly scalable with the number of views. Our technique produces the most accurate results among current algorithms for a sparse number of viewpoints according to the Middlebury datasets. Additionally, we prove to be the most efficient method among non-GPU algorithms for the same datasets. Finally, our scaled-window matching technique also excels at reconstructing deformable objects with high-curvature surfaces, which we demonstrate with a number of examples.
	Tomographic Reconstruction of Transparent Objects       PDF    MOV B. Trifonov, D. Bradley, W. Heidrich. Eurographics Symposium on Rendering 2006. (Nicosia, Cyprus) The scanning of 3D geometry has become a popular way of capturing the shape of real-world objects. Transparent objects, however, pose problems for traditional scanning methods. We present a visible light tomographic reconstruction method for recovering the shape of transparent objects, such as glass. Our setup is relatively simple to implement, and accounts for refraction, which can be a significant problem in visible light tomography.

Augmented Reality and Immersive Environments

	Augmented Reality on Cloth with Realistic Illumination D. Bradley, G. Roth, P. Bose. Machine Vision and Applications. 2009. Vol. 20, No. 2, pp 85-92. Augmented reality (AR) is the concept of inserting virtual objects into real scenes. Often, augmentations are aligned with rigid planar objects in the scene. However, a more difficult task is to align non-rigid augmentations with flexible objects like cloth. To address this problem, we present a method to perform real-time flexible augmentations on cloth. Our method involves sparse cloth-tracking in video images using a new vision-based marker system with temporal coherence. We include an image-based method to automatically acquire real world illumination and shadows from the input frame. Non-rigid augmentations are achieved by rendering a textured 2D mesh aligned with the cloth surface, and combining the illumination result.
	Natural Interaction with Virtual Objects Using Vision-Based Six DOF Sphere Tracking       PDF    AVI D. Bradley, G. Roth. Advances in Computer Entertainment Technology 2005. pp. 19-26. (Valencia, Spain). A common task in computer entertainment is the ability to interact with virtual 3D objects. Interacting with these objects using standard computer input devices such as a mouse and keyboard can often be a difficult task. We present a new tangible user interface system that includes a passive optical tracking method to determine the six degree-of-freedom (DOF) pose of a sphere in a real-time video stream, and then apply the pose to a virtual object. The pose of the sphere is accurately resolved under partial occlusions, allowing the object to be manipulated by hand without a tracking failure.
	Image-based Navigation in Real Environments Using Panoramas       PDF D. Bradley, A. Brunton, M. Fiala, G. Roth. IEEE Int. Workshop on Haptic Audio Visual Environments and their Applications 2005. (Ottawa, Canada). We present a system for virtual navigation in real environments using image-based panorama rendering. Multiple overlapping images are captured using a Point Grey Ladybug camera and a single cube-aligned panorama image is generated for each capture location. Panorama locations are connected in a graph topology and registered with a 2D map for navigation. A real-time image-based viewer renders individual 360-degree panoramas using graphics hardware acceleration. Real-world navigation is performed by traversing the graph and loading new panorama images. The system contains a user-friendly interface and supports standard input and display or a head-mounted display with an inertial tracking device.
	Adaptive Thresholding Using the Integral Image D. Bradley, G. Roth. ACM Journal of Graphics Tools. 2007. Vol 12, No. 2: 13-21. We present a technique for real-time adaptive thresholding using the integral image of the input. Our technique is an extension of a previous method. However, our solution is more robust to illumination changes in the image. Additionally, our method is simple and easy to implement. Our technique is suitable for processing live video streams at a real-time frame-rate, making it a valuable tool for interactive applications such as augmented reality.
	Distributed Table-Top AR with 3D Input       AVI D. Bradley, M. Fiala. International Symposium on Mixed and Augmented Reality (ISMAR 2005) [Demo]. (Vienna, Austria). We demonstrate a distributed augmented reality (AR) system that provides an interactive 3D workbench on a table top environment. Multiple users interact with a shared virtual world through a single controlling server and multiple rendering clients. The augmentation is aligned to a table containing ARTag fiducial markers that are used to build a robust 3D coordinate frame and determine camera poses. Users can observe using a camera connected to a PC, a head-mounted display (HMD), or using a wireless handheld device (PDA, cellular phone, etc). 3D input is achieved using a wireless mouse with markers that are tracked and registered in the table top coordinate frame. We demonstrate our system with an application where users construct a 3D city with roads, buildings and AI-driven vehicles on a virtual terrain.

Real-Time Rendering

Visualizing botanical trees over four seasons       PDF    AVI D. Bradley. IEEE Visualization 2004, pp. 13p-13p. (Austin, USA). This paper presents a method for visualizing the growth process of different botanical tree species over the four seasons of a year. The proposed method uses a data model to store a random three-dimensional tree and quickly render it using interactive 3D real-time animation. The tree model contains operations to sprout leaves and grow in the spring and summer, and to change the color of the leaves in the fall, which eventually fall off for the winter.

Evaluation of Real-Time Continuous Terrain Level of Detail Algorithms       PDF D. Bradley. Undergraduate Honours Project, Carleton University. 2003. This project is an evaluation of three real-time continuous terrain level of detail algorithms described in the papers Real-Time Generation of Continuous Levels of Detail for Height Fields by [Röttger et al., 1998], ROAMing Terrain: Real-time Optimally Adapting Meshes by [Duchaineau et al., 1997] and Visualization of Large Terrains Made Easy by [Lindstrom and Pascucci, 2001]. The evaluation and comparison of the algorithms is based on the trade-off of polygon count to terrain accuracy over four separate test data sets.

Other Stuff

• my resume
• my voronoi code - memory efficient version of Steve Fortune's voronoi program.
• old wallpaper graphics - some 3D images I made when I was first getting interested in graphics (a long time ago).
• old course projects