Acquiring Scattering Properties of Participating Media by Dilution SIGGRAPH Conference July 2006, Boston, USA Sponsors: NSF, ONR, Sloan Srinivasa Narasimhan

Acquiring Scattering Properties of Participating Media by Dilution

SIGGRAPH ConferenceJuly 2006, Boston, USA

Sponsors: NSF, ONR, Sloan

Srinivasa Narasimhan

Mohit Gupta

Carnegie MellonUniversity

Craig Donner

Henrik Wann Jensen

UC San Diego

Ravi Ramamoorthi

Shree Nayar

ColumbiaUniversity

Accurate Rendering of Media Critical for Realism

Scattering in Participating Media

Accuracy Limited by the Input Medium Parameters

Significant Progress in Volumetric Rendering

[Jensen et al, 01] [Donner, 03]

[Fedkiw et al, 01][Jensen, 02]

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

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 SetupRobust Parameter Estimation from a Photograph

Cover Entire Parameter Space

Our Measurement Setup

Camera

Glass Tank

Frosted Glass Bulb

Anti-reflection Glass

Our Measurement Setup

Dimensions of Tank: 25cm x 30 cm x 30 cm

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

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]

• Key Idea: Avoid Multiple Scattering

- Single Scattering dominant

At “low” concentrations:

- Multiple Scattering negligible

[Ishimaru 97; Narasimhan et al 99-03] Increasing Milk Concentrations

Photo of Milk in Setup

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

transport.

Single Scattering Ray Geometry

Physical Apparatus

Captured Ortho-Photo

• Range of Scattering Angles: [ 0 deg, 175 deg ]

• Range of Path-lengths: [ 125 mm, 610mm ]

• All Path-length and Angle Combinations

Source

Medium

)(xE

)(xE

Single Scattering Model and Estimation

Source

),,( zyxE ),( yxE

• Image Formation Model:

X

Y

Z

Medium

1d

2d

Phasefunction

ScatteringCoefficient

ExtinctionCoefficient

)exp( 121

0 dd

I ),( gP )exp( 2d),,( zyxE ),( yxE dz g


Source

),( yxE

||),(),(||minarg modelmeasured

,,yxEyxE

g

• Parameter Estimation: Nelder-Meade Search in Matlab

X

Y

Z

Medium

1d

2d

• Image Formation Model: Phasefunction



)exp( 121

0 dd

I ),( gP )exp( 2d),( yxE dz g


Source

),( yxE

||),(),(||minarg modelmeasured

,,yxEyxE

g

• Parameter Estimation: Nelder-Meade Search in Matlab

X

Y

Z

Medium

1d

2d

• Image Formation Model: Phasefunction



)exp( 121

0 dd

I ),( gP )exp( 2d),( yxE dz g

Unique and

Robust!

How Much to Dilute?

Multiple

Scattering

Single

Scattering 02

ln1

E

E

d

9 ml

15 ml

26 ml

MultipleScattering

SingleScattering

9 ml 18 ml 20 ml

23 ml

15 ml 26 ml

4 ml

Increasing Milk Concentration

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,…

Budweiser Coors Light Yuengling Beer Orange PowderGatorade Pink LemonadeClorox DetergentEra Detergent

Cappuccino Espresso Mint Mocha Coke Pepsi SpriteSuisse MochaLemon Tea

Apple Juice Sugar PowderRuby Gfruit Juice Grape Juice White ZinfandelCranberry Juice ChardonnayMerlot

Reg Choc MilkLow Fat 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)

Salt

Powder

Balancing

Shampoo

Strawberry

Shampoo

Heads &

Shoulders

Pacific Ocean

(Surface, 1 hr)

Orange Powder

Pink Lemonade

Powder

Regular Milk

Cappuccino Powder

Ruby Grapefruit

Juice

Low Fat Milk

Salt PowderRegular Chocolate

Milk

Espresso Coffee

Low Fat Choc Milk

Sample Photographs: Highly Scattering Media

Merlot Wine

Yuengling Beer

Era Detergent

Grape Juice

Lemon Tea

Powder

Strawberry Shampoo

Coke

Brown Sugar

Pacific Ocean Water

Chardonnay Wine

Sample Photographs: Highly Absorbing Media

Medium Volume

Extinction Coefficient () (x 10-2

mm-1)

Scattering Coefficient () (x 10-2

mm-1)

Average Cosine

(g)

Low-Fat Milk

16 ml

R 0.9126 0.9124 0.932G 1.0748 1.0744 0.902B 1.2500 1.2492 0.859

Regular Milk

15 ml R 1.1874 1.1873 0.750

G 1.3296 1.3293 0.714

B 1.4602 1.4589 0.681

Regular Chocolate

Milk16 ml

R 0.7359 0.7352 0.862

G 0.9172 0.9142 0.838

B 1.0688 1.0588 0.806

Sample Parameters: Highly Scattering Media

Medium Volume

Extinction Coefficient () (x 10-2

mm-1)

Scattering Coefficient () (x 10-2

mm-1)

Average Cosine

(g)

Yuengling Beer

2900 ml

R 0.1535 0.0495 0.969G 0.3322 0.0521 0.969B 0.7452 0.0597 0.975

Merlot Wine

1500 ml R 0.7639 0.0053 0.974

G 1.6429 0.0000 -

B 1.9196 0.0000 -

Era Detergent

2300 mlR 0.7987 0.0553 0.949

G 0.5746 0.0586 0.950

B 0.2849 0.0906 0.971

Sample Parameters: Highly Absorbing Media

•Regular Milk

•Low Fat Milk

•Regular Choc Milk

•Low Fat Choc Milk

•Coors Light

•Sprite

•Strawberry Shampoo

•Chardonnay

•Merlot Wine

•Coke

•Era Detergent

•Orange Powder•Pink

Lemonade Powder•Ruby Grape Fruit Juice

Ab

sorp

tion

Coeff

icie

nt

Scattering Coefficient

•Ocean Water

•Regular Milk

•Low Fat Milk

Ab

sorp

tion

Coeff

icie

nt




•Coors Light

•Sprite

•Chardonnay

•Merlot Wine

•Coke



Highly Scattering Media


•Era Detergent

•Ocean Water

•Regular Milk

•Low Fat Milk



•Coors Light

•Sprite

•Chardonnay

•Merlot Wine

•Coke



Highly Absorbing MediaA

bso

rpti

on

Coeff

icie

nt



•Era Detergent

•Ocean Water

•Regular Milk

•Low Fat Milk



•Coors Light•Sprite

•Chardonnay

•Merlot Wine

•Coke



Low Scattering

& Absorption

Ab

sorp

tion

Coeff

icie

nt



•Era Detergent

•Ocean Water

•Regular Milk

•Low Fat Milk



•Coors Light

•Sprite

•Chardonnay

•Merlot Wine

•Coke


Lemonade Powder•Ruby Grape

Fruit Juice

Moderate Scattering

& Absorption

Ab

sorp

tion

Coeff

icie

nt



•Era Detergent

Distance from the Source (mm)

Inte

nsi

ty (

0-2

55

)

R

G

B

Experimental Validation: Fits to Measurements

Orange Powder

Sample Fits: Highly Absorbing Media

Era Detergent Pacific Ocean Surface Water

Yuengling Beer Merlot Wine

Dist. from Source

Bri

gh

tness

Sample Fits: Highly Scattering Media

Regular Milk Low Fat Milk

Clorox Detergent Regular Chocolate Milk

Dist. from Source

Bri

gh

tness

Renderings with the

“Kitchen” Environment Map

[Debevec et al]

Merlot Wine Chardonnay Wine

Coca-ColaYuengling Beer

MilkYuengling Beer

Renderings with a Single Directional Light Source

Coca-colaYuengling Beer

Chardonnay Wine Orange Powder

Era DetergentStrawberry Shampoo

+ =

75% Espresso Light Coffee25% Milk

Blending Parameters

Blending Parameters

+ =

50% Wine 50% Milk ?

Wine Water Milk Espresso

Transitions between Media

Concentrations at which Parameters Measured

Real Concentrations

Robust Parameter Estimation

Simple Apparatus

Render Any Concentration

Mixing Media

+ =

http://graphics.cs.cmu.edu

Summary

Documents

Acquiring Scattering Properties of Participating Media by Dilution SIGGRAPH Conference July 2006, Boston, USA Sponsors: NSF, ONR, Sloan Srinivasa Narasimhan