Acquiring Scattering Properties of Participating Media by Dilution SIGGRAPH Conference

1. Acquiring Scattering Properties of Participating Media by Dilution SIGGRAPH Conference July 2006, Boston, USA Sponsors: NSF, ONR, Sloan Srinivasa Narasimhan Mohit Gupta Carnegie Mellon University Ravi Ramamoorthi Shree Nayar Columbia University Craig Donner Henrik Wann Jensen UC San Diego

2. Scattering in Participating Media Accurate Rendering of Media Critical for Realism

3. Significant Progress in Volumetric Rendering [Jensen et al, 01] [Donner, 03] [Fedkiw et al, 01] [Jensen, 02] Accuracy Limited by the Input Medium Parameters

4. Measurement Work in Graphics Attenuation of Laser Beams [Hawkins et al, 05] No Scattering Directional Scattering using a Mirror [Hawkins et al, 05] No Attenuation Diffusion-based BSSRDF Measurement [Jensen et al, 01; Joshi et al, 05] High Scattering

5. Measurement Work in Graphics Attenuation of Laser Beams [Hawkins et al, 05] No Scattering Directional Scattering using a Mirror [Hawkins et al, 05] No Attenuation Diffusion-based BSSRDF Measurement [Jensen et al, 01; Joshi et al, 05] High Scattering One Simple Setup Robust Parameter Estimation from a Photograph Cover Entire Parameter Space

6. Our Measurement Setup Camera Glass Tank

7. Frosted Glass Bulb Anti-reflection Glass Our Measurement Setup Dimensions of Tank: 25cm x 30 cm x 30 cm

8. Problem: Multiple Scattering • Causes significant Blurring of • Incident Light • Inverse Estimation is Ill-conditioned • and Not Unique [Ishimaru 75,97; McCormick et al., 79-83] Photo of Milk in Setup

9. Problem: Multiple Scattering • Causes significant Blurring of • Incident Light • Inverse Estimation is Ill-conditioned • and Not Unique [Ishimaru 75,97; McCormick et al., 79-83] Photo of Milk in Setup • Key Idea: Avoid Multiple Scattering At “low” concentrations: - Single Scattering dominant - Multiple Scattering negligible [Ishimaru 97; Narasimhan et al 99-03] Increasing Milk Concentrations

10. So…dilute media “sufficiently” with water to simplify light transport.

11. Medium Source Physical Apparatus • Range of Scattering Angles: [ 0 deg, 175 deg ] • Range of Path-lengths: [ 125 mm, 610mm ] • All Path-length and Angle Combinations Captured Ortho-Photo

12. Medium Source • Image Formation Model: Scattering Coefficient Phase function Extinction Coefficient

13. Medium Source • Image Formation Model: Scattering Coefficient Phase function Extinction Coefficient • Parameter Estimation: Nelder-Meade Search in Matlab

14. Medium Source • Image Formation Model: Scattering Coefficient Phase function Extinction Coefficient Unique and Robust! • Parameter Estimation: Nelder-Meade Search in Matlab

15. How Much to Dilute? 20 ml 4 ml 9 ml 15 ml 18 ml 23 ml 26 ml Increasing Milk Concentration Single Scattering Multiple Scattering 26 ml Single Scattering Multiple Scattering 15 ml 9 ml

16. Database of 40 Common Materials • Alcoholic Beverages – 3 wines, 3 beers… • Coffees – black, with cream, cappuccino,… • Milks – chocolate, whole, 2% fat, vitamin A & D,… • Juices – grape, apple, cranberry,… • Soft-drinks – coke, pepsi, lemonade… • Cleaning supplies – detergents, shampoos,… • Powders and Crystals – sugar, salt, tang,… • Pacific Ocean Water – bay, different depths,…

17. Gatorade Budweiser Coors Light Yuengling Beer Era Detergent Clorox Detergent Orange Powder Pink Lemonade Lemon Tea Cappuccino Espresso Mint Mocha Suisse Mocha Coke Pepsi Sprite Apple Juice Ruby Gfruit Juice Grape Juice Cranberry Juice Sugar Powder Merlot Chardonnay White Zinfandel Low Fat Choc Milk Reg Choc Milk Low Fat Milk Reduced Milk Regular Milk Low Fat Soy Milk Reg Soy Milk White Gfruit Juice Mission Bay (10ft, 8 hrs) Mission Bay (10ft, 30 mins) Mission Bay (Surface, 1 hr) Pacific Ocean (Surface, 1 hr) Salt Powder Heads & Shoulders Balancing Shampoo Strawberry Shampoo

18. Sample Photographs: Highly Scattering Media Pink Lemonade Powder Regular Chocolate Milk Low Fat Choc Milk Ruby Grapefruit Juice Salt Powder Orange Powder Low Fat Milk Espresso Coffee Cappuccino Powder Regular Milk

19. Sample Photographs: Highly Absorbing Media Coke Yuengling Beer Pacific Ocean Water Grape Juice Merlot Wine Era Detergent Chardonnay Wine Strawberry Shampoo Lemon Tea Powder Brown Sugar

20. Sample Parameters: Highly Scattering Media

21. Sample Parameters: Highly Absorbing Media

22. Merlot Wine • Coke • Era Detergent • Orange Powder Absorption Coefficient • Pink Lemonade Powder • Strawberry Shampoo • Ruby Grape Fruit Juice • Regular Choc Milk • Chardonnay • Regular Milk • Coors Light • Ocean Water • Low Fat Choc Milk • Low Fat Milk • Sprite Scattering Coefficient

23. Highly Scattering Media • Merlot Wine • Coke • Era Detergent • Orange Powder Absorption Coefficient • Pink Lemonade Powder • Strawberry Shampoo • Ruby Grape Fruit Juice • Regular Choc Milk • Chardonnay • Regular Milk • Coors Light • Ocean Water • Low Fat Choc Milk • Low Fat Milk • Sprite Scattering Coefficient

24. Highly Absorbing Media • Merlot Wine • Coke • Era Detergent • Orange Powder Absorption Coefficient • Pink Lemonade Powder • Strawberry Shampoo • Ruby Grape Fruit Juice • Regular Choc Milk • Chardonnay • Regular Milk • Ocean Water • Coors Light • Low Fat Choc Milk • Low Fat Milk • Sprite Scattering Coefficient

25. Low Scattering & Absorption • Merlot Wine • Coke • Era Detergent • Orange Powder Absorption Coefficient • Pink Lemonade Powder • Strawberry Shampoo • Ruby Grape Fruit Juice • Regular Choc Milk • Chardonnay • Regular Milk • Ocean Water • Coors Light • Low Fat Choc Milk • Low Fat Milk • Sprite Scattering Coefficient

26. Moderate Scattering & Absorption • Merlot Wine • Coke • Era Detergent • Orange Powder Absorption Coefficient • Pink Lemonade Powder • Strawberry Shampoo • Ruby Grape Fruit Juice • Regular Choc Milk • Chardonnay • Regular Milk • Coors Light • Low Fat Choc Milk • Low Fat Milk • Sprite Scattering Coefficient

28. R Intensity (0-255) G B Distance from the Source (mm) Experimental Validation: Fits to Measurements Orange Powder

29. Sample Fits: Highly Absorbing Media Brightness Dist. from Source Pacific Ocean Surface Water Era Detergent Yuengling Beer Merlot Wine

30. Sample Fits: Highly Scattering Media Brightness Dist. from Source Regular Milk Low Fat Milk Clorox Detergent Regular Chocolate Milk

31. Renderings with the “Kitchen” Environment Map [Debevec et al]

32. Merlot Wine Chardonnay Wine

33. Coca-Cola • Yuengling Beer

34. Milk • Yuengling Beer

35. Renderings with a Single Directional Light Source

36. Yuengling Beer Coca-cola

37. Orange Powder Chardonnay Wine

38. Strawberry Shampoo Era Detergent

39. Blending Parameters + = 75% Espresso 25% Milk Light Coffee

40. Blending Parameters + = 50% Wine 50% Milk ?

41. Transitions between Media Wine  Water  Milk  Espresso

42. Concentrations at which Parameters Measured

43. Real Concentrations

44. Summary = + Simple Apparatus Robust Parameter Estimation Render Any Concentration Mixing Media http://graphics.cs.cmu.edu