Derek Bradley
Department of Computer Science
University of British Columbia
PhD, University of British Columbia, 2010
MCS, Carleton University, 2005
BCS, Carleton University, 2003
bradleyd (at) cs.ubc.ca
This website is a portfolio of my research and publications, plus access to my resume and a few other things. I recently completed my PhD in Computer Science (Computer Graphics) at the University of British Columbia. My supervisor was Dr. Wolfgang Heidrich. I am interested in various capture projects, including multiview stereo, facial performance capture, and space-time reconstruction of other deforming objects.
2010
Globally Consistent Space Time Reconstruction
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T. Popa, I. South-Dickinson, D. Bradley, A. Sheffer, W. Heidrich
Computer Graphics Forum (Proceedings of Eurographics Symposium on Geometry Processing). 2010. (Lyon, France).
Most objects deform gradually over time, without abrupt changes in geometry or topology, such as changes in genus. Correct space-time reconstruction of such objects should satisfy this gradual change prior. We introduce a new method for globally consistent space-time geometry and motion reconstruction from video capture. We use the gradual change prior to resolve inconsistencies and faithfully reconstruct the geometry and motion of the scanned objects. In contrast to most previous methods our algorithm doesn’t require a strong shape prior such as a template and provides better results than other template-free approaches.
High Resolution Passive Facial Performance Capture
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D. Bradley, W. Heidrich, T. Popa, A. Sheffer
ACM Transactions on Graphics (Proceedings of SIGGRAPH). 2010. (Los Angeles, USA).
We introduce a purely passive facial capture approach that uses only an array of video cameras, but requires no template facial geometry, no special makeup or markers, and no active lighting. We obtain initial geometry using multi-view stereo, and then use a novel approach for automatically tracking texture detail across the frames. As a result, we obtain a high-resolution sequence of compatibly triangulated and parameterized meshes. The resulting sequence can be rendered with dynamically captured textures, while also consistently applying texture changes such as virtual makeup.
Binocular Camera Calibration Using Rectification Error
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D. Bradley, W. Heidrich
Proceedings of Canadian Conference on Computer and Robot Vision. 2010. (Ottawa, Canada).
Reprojection error is a commonly used measure for comparing
the quality of different camera calibrations, for example
when choosing the best calibration from a set. While
this measure is suitable for single cameras, we show that
we can improve calibrations in a binocular or multi-camera
setup by calibrating the cameras in pairs using a rectification
error. The rectification error determines the mismatch
in epipolar constraints between a pair of cameras, and it
can be used to calibrate binocular camera setups more accurately
than using the reprojection error.
2009
Synchronization and Rolling Shutter Compensation for Consumer Video Camera Arrays
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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
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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.
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. [Submitted Sept. 2005]
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.
2008
Time-resolved 3D Capture of Non-stationary Gas Flows
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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
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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
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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.
2007
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.
2006
Tomographic Reconstruction of Transparent Objects
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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.
2005
Natural Interaction with Virtual Objects Using Vision-Based Six DOF Sphere Tracking
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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
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D. Bradley, A. Brunton, M. Fiala, G. Roth
IEEE International 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.
Distributed Table-Top AR with 3D Input
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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.
2004
Visualizing botanical trees over four seasons
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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.
2003
Evaluation of Real-Time Continuous Terrain Level of Detail Algorithms
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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 [Rottger 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.