We present a novel calibration framework for multi-projector displays that achieves continuous geometric calibration by estimating and refining the poses of all projectors in an ongoing fashion during actual display use. Our framework provides scalability by operating as a distributed system of "intelligent" projector units: projectors augmented with rigidly-mounted cameras, and paired with dedicated computers. Each unit interacts asynchronously with its peers, leveraging their combined computational power to cooperatively estimate the poses of all of the projectors. In cases where the projection surface is static, our system is able to continuously refine all of the projector poses, even when they change simultaneously.

Projectors equipped with wide-angle lenses can have an advantage over traditional projectors in creating immersive display environments since they can be placed very close to the display surface to reduce user shadowing issues while still producing large images. However, wide-angle projectors exhibit severe image distortion requiring the image generator to correctively pre-distort the output image. In this paper, we describe a new technique based on Raskar's (1998) two-pass rendering algorithm that is able to correct for both arbitrary display surface geometry and the extreme lens distortion caused by fisheye lenses. We further detail how the distortion correction algorithm can be implemented in a real-time shader program running on a commodity GPU to create low-cost, personal surround environments

Using projectors to create perspectively correct imagery on arbitrary display surfaces requires geometric knowledge of the display surface shape, the projector calibration, and the user’s position in a common coordinate system. Prior solutions have most commonly modeled the display surface as a tessellated mesh derived from the 3D-point cloud acquired during system calibration. In this paper we describe a method for functional reconstruction of the display surface, which takes advantage of the knowledge that most interior display spaces (e.g. walls, floors, ceilings, building columns) are piecewise planar. Using a RANSAC algorithm to recursively fit planes to a 3D-point cloud sampling of the surface, followed by a conversion of the plane definitions into simple planar polygon descriptions, we are able to create a geometric model which is less complex than a dense tessellated mesh and offers a simple method for accurately modeling the corners of rooms. Planar models also eliminate subtle, but irritating, texture distortion often seen in tessellated mesh approximations to planar surfaces.

This paper presents PixelFlex - a spatially reconfigurable multi-projector display system. The PixelFlex system is composed of ceiling-mounted projectors, each with computer-controlled pan, tilt, zoom and focus; and a camera for closed-loop calibration. Working collectively, these controllable projectors function as a single logical display capable of being easily modified into a variety of spatial formats of differing pixel density, size and shape. New layouts are automatically calibrated within minutes to generate the accurate warping and blending functions needed to produce seamless imagery across planar display surfaces, thus giving the user the flexibility to quickly create, save and restore multiple screen configurations. Overall, PixelFlex provides a new level of automatic reconfigurability and usage, departing from the static, one-size-fits-all design of traditional large-format displays. As a front-projection system, PixelFlex can be installed in most environments with space constraints and requires little or no post-installation mechanical maintenance because of the closed-loop calibration.

In 1998 we introduced the idea for a project we call the Office of the Future. Our long-term vision is to provide a better every-day working environment, with high-fidelity scene reconstruction for life-sized 3D tele-collaboration. In particular, we want a true sense of presence with our remote collaborator and their real surroundings. The challenges related to this vision are enormous and involve many technical tradeoffs. This is true in particular for scene reconstruction. Researchers have been striving to achieve real-time approaches, and while they have made respectable progress, the limitations of conventional technologies relegate them to relatively low resolution in a restricted volume. We present a significant step toward our ultimate goal, via a slightly different path. In lieu of low-fidelity dynamic scene modeling we present an exceedingly high fidelity reconstruction of a real but static office. By assembling the best of available hardware and software technologies in static scene acquisition, modeling algorithms, rendering, tracking and stereo projective display, we are able to demonstrate a portal to a real office, occupied today by a mannequin, and in the future by a real remote collaborator. We now have both a compelling sense of just how good it could be, and a framework into which we will later incorporate dynamic scene modeling, as we continue to head toward our ultimate goal of 3D collaborative telepresence.

Large area tiled displays are gaining popularity for use in collaborative immersive virtual environments and scientific visualization. While recent work has addressed the issues of geometric registration, rendering architectures, and human interfaces, there has been relatively little work on photometric calibration in general, and photometric non-uniformity in particular. For example, as a result of differences in the photometric characteristics of projectors, the color and intensity of a large area display varies from place to place. Further, the imagery typically appears brighter at the regions of overlap between adjacent projectors. We analyze and classify the causes of photometric non-uniformity in a tiled display. We then propose a methodology for determining corrections designed to achieve uniformity, that can correct for the photometric variations across a tiled projector display in real time using per channel color look-up-tables (LUT).

Conventional projector-based display systems are typically designed around precise and regular configurations of projectors and display surfaces. While this results in rendering simplicity and speed, it also means painstaking construction and ongoing maintenance. In previously published work, we introduced a vision of projector-based displays constructed from a collection of casually-arranged projectors and display surfaces. In this paper, we present flexible yet practical methods for realizing this vision, enabling low-cost mega-pixel display systems with large physical dimensions, higher resolution, or both. The techniques afford new opportunities to build personal 3D visualization systems in offices, conference rooms, theaters, or even your living room. As a demonstration of the simplicity and effectiveness of the methods that we continue to perfect, we show in the included video that a 10-year old child can construct and calibrate a two-camera, two-projector, head-tracked display system, all in about 15 minutes.