A General-Purpose Platform for 3-D Reconstruction from Sequence of Images

1. A General-Purpose Platform for 3-D Reconstruction from Sequence of Images Ahmed Eid, Sherif Rashad, and Aly Farag Computer Vision and Image Processing Lab Department of Electrical and Computer EngineeringSpeed Scientific School University of Louisville URL: www.cvip.louisville.edu

2. Abstract The purpose of this project is two folds: 1- Propose a vision platform that lend itself for acquisition of calibrated sequence of images, and concurrently obtain a direct 3D reconstruction by laser scanning. 2- Implement the stereo- and space-carving based approaches for 3D reconstructions on a sequence of calibrated images. These reconstructions will be evaluated against the 3D scanning generated from a laser scanner.

3. System Setup • The proposed system consists of a laser scanner (Cyberware, Inc, California), on which one or more optical cameras be mounted. • The laser scanner generates a 3-D scan of an object by rotating 360 deg. • The shaft over which the scanner head is mounted can be controlled in terms of speed and angle of rotation.

4. Motion Mechanism • The field of view of the camera(s) is set to cover the same size of objects as the laser scanner. • A sequence of referenced images can be acquired by a calibrated camera(s), mounted on the shaft. • Hence, by the this setup we generate a sequence of images {I1, I2, ... In} which we use in subsequent studies on object • reconstruction

5. (I) 3-D Reconstruction Using Stereo Techniques • Find points in two or more input images that correspond to the same point in the scene. • Use knowledge of the camera locations and triangulation to determine the depth of the scene point. • One of the main problems of stereo is the correspondence problem. • To solve this problem, a large number of stereo techniques rely heavily on assumptions such as the existence of specific features in the images to produce satisfactory results

6. Epipolar Geometry of Traditional Stereo Epipolar plan 3d point X Left image plan A right epipolar line A left epipolar line xL xR eL eR CR CL Center of right camera Center of left camera xL, xR = two corresponding points eL , eR = Left and right epipols

7. Photo_consistent Photo_inconsistent (II) 3-D Reconstruction Using Space Carving • Step1: • Initialize the volume V. • Step2: • Determine the set of voxels Vis(V) on the surface of V. • Project each voxel v on Vis(V) to different images where v is visible. • Determine the photo_consistency of each voxel v on Vis(V). • Step3 • If photo_consistent detain the voxel • If photo_inconsistent carve the voxel

8. (III) 3-D Laser Scanner • The 3-D scanner used in the proposed system is the Cyberware 3030. • Its dynamic Range accommodates varying lighting conditions and surface properties. • In operation, the 3030 shines a safe, low-intensity laser on an object to create a lighted profile. • A high-quality video sensor captures this profile from two viewpoints. The system can digitize thousands of these profiles in a few seconds to capture the shape of the entire object. • Simultaneously, a second video sensor in the scanner acquires color information.

9. 3 2 1 (IV) Panoramic Stereo Cyclograph Generation C1 C2 Cm y  xo x x m-cyclograph images (n x k) x-y- Volume of input images Ik I2 I1 I1 =360 =5 =0 One Cyclograph image k-Input images (n x m)

10. Formation of Stereo cyclograph pairs m/2 2 1 L2 L1 Lm/2 R2 Rm/2 R1 xo m-cyclograph images=m/2-cyclograph pairs The two views of each pair should be overlapped to construct a cyclograph stereo pair.

11. A Cyclograph Pair

12. Scanner Stereo Space Carving Results: 3D Reconstruction

13. Results: 3D Registration SpaceCarving Scanner Stereo Scanner

14. Results: Integration Reconstruction With Errors Integration With Space Carving

15. Input Images

16. Complete Model Scanner Space Carving