Rendering Particles in the Shafts of Light

Presented by Taekyu Shin

Clear Day Foggy Day

Shaft of Light due to Light Scattering

Clear Day Foggy Day

Point Source

Surface PointViewer

Direct Transmission

Scattered (glows)

Let’s see what we can improve here

Do you see good attenuation?

• Dobashi [2000] , Dobashi [2002]– Shaft of Light

Should it be more naturally jittered?

• Dobashi [2000] , Dobashi [2002]– Shaft of Light

Another problem (Hoffman 2003)

• Works only in far view points.• No consideration for dense aerosol.– No attenuation. Where are particles?

• Close view point– challenging

My Contribution

• Good attenuation effect for shafts of light– Result : Later

• No work for natural attenuation where each particle works as a luminaire.– Bo Sun’s Airlight model(Siggraph 2005) not suited

for this.– Our Particle Radiance Method

Overview – Ray marching

Eye

Object

Eye

Object

Eye

Object

Sum( ) =

Eye

Object

Eye

Object

=

Why this method?

• This is ‘Multiple Scattering’– Dense fog exhibit strong multiple light scattering • Mark Harris [2001]

• Can you call it multiple scattering? You are just computing lighting effect from one particle in the unit space.– ‘Just’ one? Most significant particle! (Proof?)

• This model well suits our goal, too!– The particle effects. See how particle-based.

Hey, but you are still just using one sample?That is not going to work!

• If based on a well-defined probability function

Plausible

Grundland [2005]

Eye

Object

Why?

• Well attenuated based on the distance.– And the distance is based on probability.– Random distance, still overally based on probability.

• That probability represents the air we are breathing!

Each particle as a luminaire again

• The Sun is not the only light source.– Each particle becomes a light!

Eye

Object

How do we make this model?

• No over exaggeration of the luminaire intensity • Use the surface radiance model from Bo Sun[2005]

• We modified the model to :

iiairlightsurface dBRDFLL cos

ResultReal Picture(Left) My Method(Right)

Limitation and Future Work

• No Specularity

Questions?