Light Transport Lab | Charles Grassi

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Beer-Lambert Law

The Core Idea

Light intensity decreases exponentially as it travels through a medium. The equation I = I₀ · e^(-σ·d) describes this beautifully simple relationship.

Why Things Have Color

Different wavelengths absorb at different rates! Water absorbs red light faster than blue—so deep water looks blue. Blood absorbs blue/green—so it looks red.

Optical Depth Intuition

At τ = 1, about 63% of light is absorbed. At τ = 3, it's 95%. At τ = 5, 99% is gone. This is why we use log scale—the interesting stuff happens early!

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Try this: Click "Water" preset, then slowly increase the red absorption. Watch how the color strip shifts from cyan toward pure blue—this is exactly what happens as you dive deeper!

Transmittance vs Optical Depth

Red 700nm

Green 550nm

Blue 450nm

Optical Depth (τ) Transmittance

What you see as light travels deeper 0 → 10 optical depth

Surface Deep

I = I0 · e^-σ·d

Underwater - Beer-Lambert Drag to rotate

🎨 Absorption per Wavelength

Red (σ_r) 0.10

Green (σ_g) 0.20

Blue (σ_b) 0.05

💨 Scattering Properties

Particle Size 0.10 μm

Density 1.00

⚙️ View Settings

Max Optical Depth 10

✨ Explore Presets

GLSL Shader Implementation