# Surface Scattering

Surface Scattering in KostaCLOUD

Used for extremely diffusive surfaces. Perfect hemispherical scatter distribution.

- Isotropic Surface Roughness
- Ideal Diffuser.
- Only valid for perfectly diffusing materials.

$\text{BSDF}(\beta-\beta_0) = \frac{R}{\pi}$

Where

$\beta = \sin(\theta_\text{scatter})$

, $\beta_0=\sin(\theta_\text{scatter})$

where R is the reflectivity of the sample.These values below were provided by the reference below, and re-presented here. These values are built into the "Simplistic Presets", where the idea of this table for this model in Rich Pfisterer's words: "Approximated Scatter Model"

Surface | R |
---|---|

Ideal diffuser | 1 |

Typical matte paper at normal incidence | 0.85 |

Typical diffuse black paint at normal incidence | 0.5 |

Perfect absorber | 0 |

- 1.J. E. Harvey,
*Understanding surface scatter phenomena: A linear systems formulation*, SPIE Press, Bellingham (2019).

Used for approximating smooth surface finishes.

- Isotropic Surface Roughness
- RMS Surface Roughness$\ll \lambda$(Smooth Surfaces)
- Surface Roughness is Bandwidth Limited. I.e. The roughness is not just a single sinusoidal frequency, but a spread of frequencies about some dominant frequency.
- Simplistic Model, Ideal for quick turn-around. Wavelength dependence, and model parameters may differ from reality.

$\text{BSDF}(\beta-\beta_0) = \frac{A}{B+(\beta-\beta_0)^g}$

Where

$\beta = \sin(\theta_\text{scatter})$

, $\beta_0=\sin(\theta_\text{scatter})$

with some fitting parameters: A,B, and g.These values below were provided by the reference below, and re-presented here. These values are built into the "Simplistic Presets", where the idea of this table for this model in Rich Pfisterer's words: "Approximated Scatter Model"

Mirrors

Lenses

Polish | g | B | A |
---|---|---|---|

Super | 2.5 | 0.00001 | $1.4\:(\frac{\sigma}{\lambda})^2$ |

Slightly better than Standard | 2.0 | 0.0001 | $5.46\:(\frac{\sigma}{\lambda})^2$ |

Standard | 1.5 | 0.001 | $13.92\: (\frac{\sigma}{\lambda})^2$ |

Slightly worse than Standard | 1.0 | 0.01 | $25.51\: (\frac{\sigma}{\lambda})^2$ |

Polish | g | B | A |
---|---|---|---|

Super | 2.5 | 0.00001 | $0.35\:(\frac{\sigma\Delta n}{\lambda})^2$ |

Slightly better than Standard | 2.0 | 0.0001 | $1.37\:(\frac{\sigma\Delta n}{\lambda})^2$ |

Standard | 1.5 | 0.001 | $3.50\:(\frac{\sigma\Delta n}{\lambda})^2$ |

Slightly worse than Standard | 1.0 | 0.01 | $6.35\: (\frac{\sigma\Delta n}{\lambda})^2$ |

J. E. Harvey,

*Understanding surface scatter phenomena: A linear systems formulation*, SPIE Press, Bellingham (2019).

J. E. Harvey,

*Understanding surface scatter phenomena: A linear systems formulation*, SPIE Press, Bellingham (2019).

*Understanding surface scatter phenomena: A linear systems formulation*, SPIE Press, Bellingham (2019).

*Understanding surface scatter phenomena: A linear systems formulation*, SPIE Press, Bellingham (2019).

Last modified 3mo ago