Reflection models i
Download
1 / 25

Reflection Models I - PowerPoint PPT Presentation


  • 152 Views
  • Updated On :

Reflection Models I. Today Types of reflection models The BRDF and reflectance The reflection equation Ideal reflection and refraction Fresnel effect Ideal diffuse Next lecture Glossy and specular reflection models Rough surfaces and microfacets Self-shadowing

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Reflection Models I' - venice


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Reflection models i l.jpg
Reflection Models I

  • Today

    • Types of reflection models

    • The BRDF and reflectance

    • The reflection equation

    • Ideal reflection and refraction

    • Fresnel effect

    • Ideal diffuse

  • Next lecture

    • Glossy and specular reflection models

    • Rough surfaces and microfacets

    • Self-shadowing

    • Anisotropic reflection models

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Reflection models l.jpg
Reflection Models

  • Definition: Reflection is the process by which light incident on a surface interacts with the surface such that it leaves on the incident side without change in frequency.

  • Properties

    • Spectra and Color [Moon Spectra]

    • Polarization

    • Directional distribution

  • Theories

    • Phenomenological

    • Physical

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Types of reflection functions l.jpg
Types of Reflection Functions

  • Ideal Specular

    • Reflection Law

    • Mirror

  • Ideal Diffuse

    • Lambert’s Law

    • Matte

  • Specular

    • Glossy

    • Directional diffuse

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Materials l.jpg
Materials

Plastic

Metal

Matte

From Apodaca and Gritz, Advanced RenderMan

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


The reflection equation l.jpg
The Reflection Equation

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


The brdf l.jpg
The BRDF

  • Bidirectional Reflectance-Distribution Function

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


The bssrdf l.jpg
The BSSRDF

  • Bidirectional Surface Scattering Reflectance-Distribution Function

Translucency

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Gonioreflectometer l.jpg
Gonioreflectometer

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Properties of brdf s l.jpg
Properties of BRDF’s

  • 1. Linearity

  • 2. Reciprocity principle

From Sillion, Arvo, Westin, Greenberg

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Properties of brdf s10 l.jpg
Properties of BRDF’s

  • 3. Isotropic vs. anisotropic

  • 4. Energy conservation

Reciprocity and isotropy

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Energy conservation l.jpg
Energy Conservation

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


The reflectance l.jpg
The Reflectance

  • Definition: Reflectance is ratio of reflected to incident power

  • Conservation of energy: 0 <r< 1

  • 3 by 3 set of possibilities:

  • Units: r [dimensionless], fr [1/steradians]

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Law of reflection l.jpg
Law of Reflection

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Ideal reflection mirror l.jpg
Ideal Reflection (Mirror)

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Snell s law l.jpg
Snell’s Law

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Law of refraction l.jpg

Total internal reflection:

Law of Refraction

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Optical manhole l.jpg
Optical Manhole

Total internal reflection

From Livingston and Lynch

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Fresnel reflectance l.jpg
Fresnel Reflectance

Metal (Aluminum)

Dielectric (N=1.5)

Gold F(0)=0.82

Silver F(0)=0.95

Glass n=1.5 F(0)=0.04

Diamond n=2.4 F(0)=0.15

Schlick Approximation

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Experiment l.jpg
Experiment

  • Reflections from a shiny floor

From Lafortune, Foo, Torrance, Greenberg, SIGGRAPH 97

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Cook torrance model for metals l.jpg

Approximated Reflectance

Cook-Torrance approximation

Cook-Torrance Model for Metals

Reflectance of Copper as a

function of wavelength and

angle of incidence

Measured Reflectance

Light spectra

Copper spectra

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Ideal diffuse reflection l.jpg

Lambert’s Cosine Law

Ideal Diffuse Reflection

  • Assume light is equally likely to be reflected in any output direction (independent of input direction).

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Diffuse reflection l.jpg
“Diffuse” Reflection

  • Theoretical

    • Bouguer - Special micro-facet distribution

    • Seeliger - Subsurface reflection

    • Multiple surface or subsurface reflections

  • Experimental

    • Pressed magnesium oxide powder

    • Almost never valid at high angles of incidence

  • Paint manufactures attempt to create ideal diffuse

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Phong model l.jpg
Phong Model

R(E)

E

R(L)

E

N

N

L

L

Reciprocity:

Distributed light source!

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Phong model24 l.jpg

s

Phong Model

Diffuse

Mirror

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


Properties of the phong model l.jpg
Properties of the Phong Model

  • Energy normalize Phong Model

University of Texas at Austin CS395T - Advanced Image Synthesis Spring 2007 Don Fussell


ad