1. Semi-Automatic Topology Independent Contour-Based 2 1/2 D Segmentation Using Live-Wire Semi-Automatic Topology Independent Contour-Based 2 1/2 D Segmentation Using Live-Wire Michael Knapp, Armin Kanitsar and Meister Eduard Gröller Computer Graphics Group Vienna University of Technology

2. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 2 / 14 Overview n Motivation n Live-Wire n Segmentation Process n Cross-Sections n Surface Reconstruction n Results

3. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 3 / 14 Motivation Segmententation of objects with... n homogeneous contour n inhomogeneous internal structure

4. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 4 / 14 Live-Wire Interactive contour finding method n Fixed start point n Interactively moveable end point n Calculation of lowest cost path

5. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 5 / 14 Segmentation Process Overview 1.Selection of orthogonal cross sections 2.Manual contour tracing 3.Automatic reconstruction of the object surface 4.Visualization

6. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 6 / 14 Segmentation Process (1/2) The user defines a set of cross-sections through the object and traces the contours

7. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 7 / 14 Segmentation Process (2/2) The surface is reconstructed from the traced contours

8. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 8 / 14 Surface Reconstruction (1/4) A B D E F C 2. Create connectivity graph for each slice... 1. A B C D E F

9. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 9 / 14 Surface Reconstruction (2/4) Edges are sorted by angle around the center of each area. Every area is convex. Every second outgoing edge - beginning from the incoming edge – is evaluated: The edge with the lowest average cost per pixel is selected as successor.

10. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 10 / 14 Surface Reconstruction (3/4) The connectivity graph is an Eulerian graph: n All vertices have an even number of adjacent edges n Graph contains a closed path containing each edges exactly once n Successor selection heuristics avoids crossing paths  Graph can always be decomposited into non-crossing closed pathscircuits.

11. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 11 / 14 Surface Reconstruction (4/4) A B C D E F F A B D E C... and reconstruct the outline

12. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 12 / 14 Threshold (1400)Contour-Based Results (1/2)

13. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 13 / 14 Results (2/2) Threshold Region growing Our method

14. WSCG 2004 - Michael Knapp: Contour-Based 2 ½ D Segmentation using Live-Wire 14 / 14 Thank You for Your Attention !