Building Reconstruction

Automatic Modeling of Planar-Hinged Buildings Ignacio Garcia-Dorado and Daniel Aliaga. Proceedings of Eurographics 2013.

Abstract:
We present a framework to automatically model and reconstruct buildings in a dense urban area. Our method is robust to noise and recovers planar features and sharp edges, producing a water-tight triangulation suitable for texture mapping and interactive rendering. Building and architectural priors, such as the Manhattan world and Atlanta world assumptions, have been used to improve the quality of reconstructions. We extend the framework to include buildings consisting of arbitrary planar faces interconnected by hinges. Given millions of initial 3D points and normals (i.e., via an image-based reconstruction), we estimate the location and properties of the building model hinges and planar segments. Then, starting with a closed Poisson triangulation, we use an energy-based metric to iteratively refine the initial model so as to attempt to recover the planar-hinged model and maintain building details where possible. Our results include automatically reconstructing a variety of buildings spanning a large and dense urban area, comparisons, and analysis of our method. The end product is an automatic method to produce watertight models that are very suitable for 3D city modeling and computer graphics applications.

Inverse Design of Urban Procedural Models

Inverse Design of Urban Procedural Models Carlos A. Vanegas, Ignacio Garcia-Dorado, Daniel Aliaga, Bedrich Benes, Paul Waddell ACM Transactions on Graphics (also in Proceedings SIGGRAPH Asia).

Abstract:
We propose a framework that enables adding intuitive high-level control to an existing urban procedural model. In particular, we provide a mechanism to interactively edit urban models, a task which is important to stakeholders in gaming, urban planning, mapping, and navigation services. Procedural modeling allows a quick creation of large complex 3D models, but controlling the output is a wellknown open problem. Thus, while forward procedural modeling has thrived, in this paper we add to the arsenal an inverse modeling tool. Users, unaware of the rules of the underlying urban procedural model, can alternatively specify arbitrary target indicators to control the modeling process. The system itself will discover how to alter the parameters of the urban procedural model so as to produce the desired 3D output. We label this process inverse design.

The UrbanVision System

UrbanVision is an open source software system for visualizing alternative land use and transportation scenarios at scales ranging from large metropolitan areas to individual neighborhoods. The motivation behind this system to fill the gap between the outputs of existing land use and transportation models and the automatic generation of 3D urban models and visualizations. The project is a collaborative effort between University of California Berkeley and Purdue University, led by Prof. Paul Waddell (Berkeley) and by Profs. Daniel Aliaga and Bedrich Benes (both at Purdue). The initial system is deployed to the San Francisco Bay Area CA, spanning over 7 million people and 1.5 million parcels of land.

My contribution:
UrbanVision supports automatically generating a plausible set of 3D building envelope models based on GIS input and simulation outputs. We use this information to create a set of parametric building types (e.g., 14 in the case of San Francisco), which are configured using parameters to depict a rich variety of building geometries. While each base type (e.g., school, big-retail buildings, offices, etc.) captures common structural characteristics, in total a much larger number of building styles are possible due to the parameterization. The control parameters, such as number of stories, footprint geometry, square footage, and frontage, are derived from the underlying parcel information. If there is not enough information in a parcel to derive a building geometry, heuristics are applied from nearby properties to determine a best guess.

Projector-Camera Systems

Fully Automatic Multi-Projector Calibration with an Uncalibrated Camera Ignacio Garcia-Dorado and Jeremy Cooperstock. CVPR Workshop on Projector-Camera Systems (PROCAMS'11).

Abstract:
Multiple video projectors can be used to provide a seamless, undistorted image or video over one or more display surfaces. Correct rendering requires calibration of the projectors with respect to these surface(s) and an efficient mechanism to distribute and warp the frame buffer data to the projectors. Typically, the calibration process involves some degree of manual intervention or embedding of optical sensors in the display surface itself, neither of which is practical for general deployment by non-technical users. We show that an effective result can in fact be achieved without such intervention or hardware augmentation, allowing for a fully automatic multi-projector calibration that requires nothing more than a low-cost uncalibrated camera and the placement of paper markers to delimit the boundaries of the desired display region. Both geometric and intensity calibration are performed by projection of graycoded binary patterns, observed by the camera. Finally, the frame buffer contents for display are distributed in real time by a remote desktop transport to multiple rendering machines, connected to the various projectors