1. Real-Time Ray Tracing 3D Modeling of the Future Marissa Hollingsworth Spring 2009

2. OBJECTIVES Current method: Rasterization What is Ray Tracing? Ray tracing Algorithm Applications Why ray tracing? Why not? Conclusions Questions?

3. Current Method: Rasterization Current leader for rendering 3D graphics Implemented on most standard GPUs – Meaning speed and efficiency Takes one triangle at a time, projects it to the screen and paints all covered pixels – linear complexity with respect to scene size: – Requires additional shading/shadow/texture algorithms

4. What is Ray Tracing? Technique for rendering 3D graphics Accurately imitates properties of light rays – Reflection, Refraction, Shadows Allows for global illumination

5. http://www.oyonale.com/modeles.php?lang=en&page=40

6. Ray Tracing Algorithm Viewpoint Image Light Source Scene Object 1.Scene Description 2.Ray Generation 3.Ray Traversal 4.Object intersection 5.Shadow rays 6.Recursive reflection and refraction rays 7.Pixel coloring

7. Applications: Video Games OasenQuake III Collision detection using rays Simple code for realistic effects First game using ray tracing Complex illumination model for daytime, weather conditions etc.

8. Interactive Global Illumination Simulating global lighting through tracing rays Greatly increases realism by adding global lighting effects Wald, I., Kollig, T., Benthin, C., Keller, A., and Slusallek, P. 2002. Interactive global illumination using fast ray tracing. WithWithout

9. Massive Modeling Can render entire CAD models without simplification Scales logarithmically with scene size

10. Why Ray Tracing? Highly realistic images Physical correctness and dependability Ease of implementation Highly efficient – Parallel computations Ray reuse (i.e. distance detection)

11. VW Beetle With Correct Shadows and Reflections Slusallek, P., Shirley, P., Mark, W., Stoll, G., and Wald, I. 2005. Introduction to real-time ray tracing. In SIGGRAPH '05: ACM SIGGRAPH 2005 Courses. ACM, New York, NY, USA, 1.

12. Why Not? Slow rendering times Not fully supported in hardware…yet – Mostly implemented in software – Programmable RPU (Ray processing unit) Computationally expensive!

13. Summary Ray tracing renders highly realistic 3D models Allows for efficient computations, but SLOW Many useful applications Not feasible for real time implementation in near future…but eventually!

14. QUESTIONS?