1. 1 Dr. Scott Schaefer Ray Tracing

2. 2/42 Ray Tracing Provides rendering method with  Refraction/Transparent surfaces  Reflective surfaces  Shadows

3. 3/42 Ray Tracing Provides rendering method with  Refraction/Transparent surfaces  Reflective surfaces  Shadows Image taken from http://radsite.lbl.gov/radiance/book/img/plate10.jpg

4. 4/42 Ray Tracing Provides rendering method with  Refraction/Transparent surfaces  Reflective surfaces  Shadows Image taken from http://www.tjhsst.edu/~dhyatt/superap/samplex.jpg

5. 5/42 Ray Tracing Provides rendering method with  Refraction/Transparent surfaces  Reflective surfaces  Shadows

6. 6/42 Essential Information for Ray Tracing Eye point Screen position/orientation Objects  Material properties  Reflection/Refraction coefficients  Index of refraction Light sources

7. 7/42 Recursive Ray Tracing For each pixel  Intersect ray from eye through pixel with all objects in scene  Find closest (positive) intersection to eye  Compute lighting at intersection point  Recur for reflected and refracted rays (if necessary)

8. 8/42 eye screen

9. 9/42 eye screen

10. 10/42 eye screen

11. 11/42 eye screen normal

12. 12/42 Ray Casting Removes hidden surfaces Per-pixel lighting computations

13. 13/42 Shadows Cast a virtual ray to each light source If ray hits an opaque object before the light, then omit contribution of that light If ray hits a semi-transparent object, scale the contribution of that light and continue to look for intersections Note: objects may be self-shadowing!!!

14. 14/42 shadow ray normal eye screen

15. 15/42 Shadows

16. 16/42 Shadows

17. 17/42 normal eye screen reflected ray

18. 18/42 normal eye screen shadow ray reflected ray normal

19. 19/42 normal reflected ray eye screen normal reflected ray

20. 20/42 Reflection Mirror-like/Shiny objects Surface

21. 21/42 eye screen normal refracted ray

22. 22/42 Refraction Bending of light caused by different speeds of light in different medium Each (semi-)transparent object has an index of refraction c i Use Snell’s law to find refracted vector Image taken from http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr2.html

23. 23/42 Snell’s Law Surface

24. 24/42 Snell’s Law Surface

25. 25/42 Snell’s Law Surface

26. 26/42 Snell’s Law Surface

27. 27/42 Snell’s Law Surface

28. 28/42 Snell’s Law Surface

29. 29/42 Snell’s Law Surface

30. 30/42 Snell’s Law Surface

31. 31/42 Snell’s Law Surface

32. 32/42 Snell’s Law Surface

33. 33/42 Total Internal Reflection Surface

34. 34/42 Recursive Ray Tracing Truncate at finite depth!

35. 35/42 Recursive Ray Tracing Recur for reflective/transparent objects

36. 36/42 Recursive Ray Tracing Recur for reflective/transparent objects

37. 37/42 Optimizations Lots of rays to cast! Ray-Surface intersections are expensive Associate with each object  Bounding box in 3-space If ray doesn’t intersect box, then ray doesn’t intersect object

38. 38/42 Parallel Processing Ray tracing is a trivially parallel algorithm!  Cast rays in parallel  Cast reflection, refraction, shadow rays in parallel  Calculate ray/surface intersections independently in parallel

39. 39/42 Ray Tracing: Special Effects copyright Newline Cinema

40. 40/42 Ray Tracing: Video Games

41. 41/42 Ray Tracing: Massive Models

42. 42/42 Extensions of Ray Tracing Only considers totally specular interactions  rays either reflect perfectly or refract perfectly Ray traced scenes don't show “color bleed”