1. An Efficient Method for Volume Rendering using Perspective Projection
Paper by: Kevin L. Novins, Francois X. Sillion and Donald P. Greenberg
Presentation by: Ilya Braude

2. Introduction Perspective vs. Orthogonal projection Volume Data
Space and time efficiency
Non-uniform sampling

3. Volume Rendering What is volume rendering? 3D grids of
Volume densities
Scalar fields
Ray entire volume

4. Previous Approaches Random access memory Transformation Cell-by-cell
Expensive
Cell-by-cell
Access to slices along any axis

5. Proposed Approach
Slice by slice ray tracing
Adaptive supersampling

6. Slice by Slice Ray Tracing
Data driven rays
Slabs
One slab processed at a time
Trilinear interpolation at sample points -- 2 slices at at time == slab

7. Slice by Slice Ray Tracing

8. Slice by Slice Ray Tracing
Slab processing order
Assume slabs perpendicular to Z axis
Process +Z, -Z

9. Slice by Slice Ray Tracing
Complexity
O(m2) + O(n2)
m - screen resolution
n - data resolution
Single pass through dataset

10. Sampling
Loss of resolution at rear of scene
Undersampling!!!

11. Supersampling Shoot more rays Use 3D mipmap Wastes computation
Increases complexity and interpolation

12. Adaptive Supersampling
Split rays as they progress through scene
Average results
Rays split when 3D sampling rate reaches threshold

13. Lens Effects
Possible to “focus” camera

14. Results

15. Results

16. Conclusion
Questions?
Thank you