D digitizing cameras available for applications like the museum, such as the ColorScan and the Virtuoso shape cameras. The latter uses six digital cameras, five black and white cameras for capturing the shape information and one color camera which acquires texture information which is layered onto the triangle mesh. Our digitization process begins with models acquired from photographs, using a semiautomatic system to infer complex 3-D shapes from photographs developed at IMSC (Chen, 1998, 1999). Images are used as the rendering primitives, beginning with six input images of our "teapots" at 60 degrees separation; multiple input pictures are allowed, taken from nearby viewpoints with different position, orientation and camera focal length. Other comparable approaches to digitizing museum objects (e.g., Synthonics) use an older version of the shape-from-stereo technology which requires the cameras to be calibrated whenever the focal length or relative position of the two cameras is changed. The direct output of the IMSC program is volumetric but is converted to a surface representation for the purpose of graphic rendering. The reconstructed surfaces are quite large, on the order of 40 MB. They are decimated with a modified version of a program for surface simplication using quadric error metrics written by Garland and Heckbert (1997). Figure 3. Teapot digitization: 1 of six input views; an image of the reconstructed point set; an image of the omnidirectional solid model (reconstructed surface)Pai and Reissell(1997) report on a technique based on wavelets for multiresolution modeling of 2D shapes. The models rely on a robust edge detector to detect boundary curves in the image. These curves are then rendered as solid objects using a haptic interface. The system also incorporates a fast contact detection algorithm based on collision trees. The paper includes a discussion of a state machine that serves as a simple model for contact transitio...
