To the Graduate Council: I am submitting herewith a thesis written by ...

Chapter 3: Data Collection and Modeling 36A polygonal mesh is a piece-wise linear surface that comprises vertices, edges andfaces. A vertex is a 3D point on the surface, edges are the connections between twovertices, and a face is a closed sequence of edges. In a polygonal surface mesh, anedge can be shared by, at most, two adjacent polygons and a vertex is shared by atleast two edges. We use triangle meshes to represent the discrete approximations to3D surfaces. A triangle mesh is a pair T= where ν={ν 1 ,ν 2 ,ν 3 ,….,ν n } is a set ofvertices, and τ ={τ 1 ,τ 2 ,…,τ m }is the set of triangles that approximate the surface.3.2.2 Modeling Automotive Scenes for Under Vehicle InspectionUnder ideal laboratory conditions, data collection with a range scanner isstraightforward. Underneath a vehicle however, we address several challenges. Themost significant of those is the design of the scanning mechanism. The field of view islimited by the ground clearance and the huge variation in size of the components thatmake up the scene under the vehicle. The distance (range) is too small for the use oftime-of-flight scanners and laser triangulation scanners but too large forphotogrammetric measurements.Real-time 3D data acquisition is a research challenge in computer vision. Before westart thinking of a robot mountable design for vehicle inspection, we would like tobriefly survey 3D data acquisition systems that optimize the process of digitization ofreal world scenes and objects for speed and accuracy. One such expensive effort is thedigitization of statues in the “Digital Michelangelo” project that involves the closescanning of statues for cultural heritage recording. Levoy et al. in [Levoy et al., 2000]suggest a configuration for high speed laser triangulation that involves a lightprojector recording video, that is processed later to fill holes and registered using theICP algorithm for the complete 3D model. The paper [Takatsuka et al., 1999] proposesa low cost interactive active monocular range finder. Davis and Chen [Davis andChen, 2001] present the design of a laser range scanner designed for minimumcalibration complexity. They specifically state that despite the simple geometry andcomponents, laser scanners must be engineered and calibrated with extremely highprecision. Champleboux et al. [Champleboux et al., 1992] examine the process ofregistration of multiple 3D data sets obtained with a laser range finder. They propose anew sensor calibration technique based on the conjunction of a mathematical cameramodel and further discuss an algorithm based on octree splines for recovering rigidtransformation, for rotational and translational rectification between two 3D data setsobtained from the range sensor. Having considered so many options and as a tradeoffbetween resolution and field of view we decided to jack the vehicle up by a meter anduse the inverted triangle mechanism for scanning. We calibrated the sensorarrangement as discussed in Section 3.1.2 and without disturbing it we inverted it andmoved the sensor arrangement on a conveyer belt to reconstruct the 3D scene.