Efficient Rendering of Anatomical Tree Structures Using Geometry Proxy

1. Efficient Rendering of Anatomical Tree Structures Using Geometry Proxy Hang Dou*, Christian Bauer**, Chris Wyman*, Reinhard R. Beichel** *Dept. of Computer Science, The University of Iowa **Dept. of Electrical and Computer Engineering, The University of Iowa

2. Introduction • Motivation Vessel tree structures

3. Introduction • Motivation • 1. Volume based method. • 2. Tree skeleton (center line) based method.

4. Introduction • Motivation Isosurface Volume rendering

5. Introduction • Motivation Limits of volume based method

6. Introduction • Motivation Standard truncated cone mesh (SCM) Surface convolution [Oeltze 2003]

7. Introduction • Our Method: rendering tubular tree through geometry proxy. • Does not involve pre-computation for surface reconstruction. • Smooth result with low mesh complexity. • Runs faster than rendering meshes generated from surface reconstruction methods.

8. Method Overview

9. Method Overview

10. Method Overview

11. Method Overview

12. Quad Generation • Observation: The projection of a truncated cone can be covered by the projection of a quad.

13. Quad Generation

14. Quad Generation

15. Quad Generation

16. Quad Generation

17. Quad Generation

18. Quad Generation • Gap filling

19. Quad Generation

20. Primitive Ray Intersection

21. Rendering Result

22. Primitive Ray Intersection

23. Rendering Result

24. Further Optimization • When handle dense data in which the center line points are very close to each other, we only draw the sphere. • We get about 10% speed up.

25. Further Optimization • We use CG compiler to monitor the number of instructions in OpenGL shaders. • Number of instructions: Before optimization: • Vertex shader: 21 Geometry shader: 240 Fragment shader: 306 After optimization: Vertex shader: 13 Geometry shader: 132 Fragment shader: 186

26. Results • Test environment: • Linux (C++/OpenGL/GLSL) • Intel Xeon X5450 CPU@3.0GHz • NVIDIA GTX 550 Ti

27. Results Isosurface Isosurface with QSlim Our Method SCM with 8 points SCM with 8 points SCM with 8 points Airway tree of rat lung with 35,603 center line points

28. Results Isosurface Isosurface with QSlim Our Method SCM with 8 points SCM with 8 points SCM with 8 points Vascular structure from human lung CT scan with 353,875 center line points

29. Future Work • Ray primitive intersection is computational intense. • When handle data with high depth complexity, we implement 2 pass rendering. • Get depth information. • Shade the tubular structure.

30. Questions and Comments