3D PROJECTION AND
TANGIBLE 3D TABLETOPS
3D projection installations are basedon having an accurate 3D model of thephysical part of the installation. In thevirtual 3D world, we can produce digitalcontent corresponding to the shape ofa physical object. By positioning andcalibrating the projection system sothat the relationship of the projectionto the physical object corresponds tothe virtual camera’s relationship to the3D model, we can project the digitalmodel onto the physical elements of theinstallation, thereby augmenting thephysical object (Figure 1).
As shown in Figure 2, the tangible3D tabletops developed by our researchlaboratory typically consist of atranslucent table surface under whichtwo cameras ( 1) and two projectors ( 2)are mounted [ 2]. Above the table, twoor more projectors ( 3) are mounted. Theprojector beneath the table displaysthe content on the table, while theprojectors mounted above the tableproject content onto tangibles. Thetangibles are fitted with visual markersbeneath their bases, tracked by thecameras ( 1) and tracking softwaresimilar to that found in the well-knownReactivision software [ 5]. However, thesoftware has been custom developed inorder to provide increased precision andfaster feedback so as to minimize pixelbleeding and interaction lag.
TANGIBLE URBAN PLANNING
Tangible Urban Planning [ 7] exploreshow 3D tabletops can supportcollaborative activities in urbanplanning and development projects,including participatory activities[ 6, 8]. On the tabletop surface weproject a road map representing theneighborhood designated for the urbanplanning process. We operate withtwo kinds of tangibles: cuboids, whichrepresent buildings, and cylinders ,which function as controls. The cuboidsare white, but when placed on the table,color and facade elements are projectedonto them (Figure 3). As part of theinstallation, we have added an extradisplay that visualizes a first-personcamera view into the virtual world.
Cuboids can be placed on the tablesurface and moved around while thecamera view is updated in real time onthe separate display.
In addition to the cuboids, we havethree types of cylinders. The first
In Tangible Urban Planning, the tangibles
can be employed simultaneously, which
allows multiple users to collaborate on
positioning buildings, try out different
color variations, and see the first-person
view at different times of the day.
Figure 1. Principles of 3D projection.
Figure 2. The main components of the tangible 3D tabletop.