Event Location: NSH 1507

Abstract: This talk is an overview of three recent results on 3D shape capture
using active illumination schemes.

In “Multi-Flash 3D Photography” we exploit the depth discontinuity
information captured by a multi-flash camera as an object moves along a
known path to reconstruct the shape of the object. In contrast to
existing shape-from-silhouette algorithms, this method can reconstruct
the position and orientation of points located deeper inside
concavities. Since more information than what silhouettes provide is
used, the resulting shapes are a much tighter fit to the surface of the
scanned object than a visual hull. However, points which do not produce
an observable depth discontinuity cannot be recovered. The resulting
point cloud is unevenly sampled, with very low sampling rate in shallow
concavities or flat areas. A polygon mesh model is reconstructed by
fitting an isosurface to the oriented point cloud, and an appearance
model is obtained by fitting a Phong reflectance model to the BRDF
samples using the visibility information provided by the implicit
surface.

In “Surround Structured Lighting for Full Object Scanning” we describe a
system for acquiring complete 3D surface models using a single
structured light projector, a pair of planar mirrors, and one or more
synchronized cameras. We project structured light patterns that
illuminate the object from all sides (not just the side of the
projector) and are able to observe the object from several vantage
points simultaneously. This system requires that projected planes of
light be parallel, and so we construct an orthographic projector using a
Fresnel lens and a commercial DLP projector. This configuration
achieves full 360 degree reconstructions using a single structured light
sequence, and eliminates the need for merging multiple scans or
multiplexing several projectors.

In “3D Slit Scanning With Planar Constraints” we present a planarity
constraint and a novel 3D point reconstruction algorithm for a
multi-view laser range slit scanner. The constraint is based on the fact
that all observed points on a projected laser line lie on the same plane
of laser light in 3D. The parameters of the plane of laser light
linearly parametrize a homography between a pair of images of the laser
points. This homography can be recovered from point correspondences
derived from epipolar geometry. The use of the planar constraint reduces
outliers in the reconstruction and allows for the reconstruction of
points seen in only one view.