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Stephen H. Westin

104 Eastern Heights Drive
Ithaca, NY 14850

I am currently employed at GrammaTech, Inc. where I am involved in static code analysis. Until May, 2014, I worked at Doron Precision Systems, Inc. where I dealt with visual simulation and vehicle dynamics. Until August 18, 2005, I was responsible for the Light Measurement Laboratory of the Program of Computer Graphics.


Year Institution Degree
1992 Cornell University Master of Science
1980 University of Michigan Bachelor of Science in Engineering
(Computer Engineering)


Years Organization Responsibilities
GrammaTech, Inc.
Developed and tested static analysis checks to enforce coding standards.
Doron Precision Systems, Inc.
Developed new graphics software for interactive driving simulators. Consulted on hardware and software requirements. Assisted in maintaining and improving visual models for real-time display.
2005-2007 Animusic LLC, Lansing, NY Teamed with 1 other programmer to reimplement interactive application for animation and music production. Implemented real-time display using Open Scene Graph; partnered in creating custom skins for GUI using Qt toolkit; installed RenderMan render farm on 13-node cluster.
1997-2005 Cornell University Program of Computer Graphics Head of Light Measurement Lab
1992-1997 Ford Motor Company, Dearborn, MI Supported electronic tools for creative design.
Produced HDTV renderings for market research and design evaluation.
Consulted on rendering and design issues.
1987-1990 Ford-Werke AG, Köln, Germany Coordinated development of CDRS CAD system for design studios.
Wrote specifications for CDRS and other development in collaboration with Ford personnel in U.S. and England.
1984-1987 Ford Motor Company, Dearborn, MI Researched advanced electronic tools for creative design.
1983-1984 Ford Motor Company, Dearborn, MI (contractor) Supported visualization software for structural analysis.
1975-1983 Environmental Research Institute of Michigan System programming and management of VAX and PDP-11 systems.
Supported software for remote sensing: image processing and atmospheric optics simulation.

Research Interests

All the areas mentioned below share a common thread: they are concerned with measurement and representation of appearance.

Subsurface Scattering

I have been active in measuring and modeling the optics of human skin and similar surfaces where subsurface scattering is visually important. Our array of 13 high-resolution digital still cameras will allow us to capture the light scattered in many directions from the face (or other body part) of a human subject. We plan to use the data thus obtained to test and verify new models of subsurface scattering, specifically for media composed of several different layers and with visible spatial variations.

Psychophysics of Material and Shape Perception

Much work has gone on in studying the physical accuracy of reflectance models, but the nagging feeling remains that perceptible differences between surfaces are not well represented by physical measurements. I worked with Jim Ferwerda to find ways to convert physical measurements into relevant perceptual metrics.


The most elaborate device in the Laboratory is our gonioreflectometer, a device for measuring the bidirectional reflectance distribution function (BRDF) of flat samples. It is capable of measuring across the visible spectrum from 400-700nm with a resolution of approximately 5nm per sample. It is usable only on isotropic surfaces, but can measure at angles out to at least 85° from the surface normal. This device was built by Sing-Choong Foo as part of his Master's thesis.

Camera-Based BRDF Measurement

Image-Based BRDF Measurement Including Human Skin, a paper by Steve Marschner and others (including me) on how to measure the BRDF of a curved object using only a good digital camera, an electronic flash, and a Cyberware scanner. This is a PDF file distilled from the actual PostScript® file submitted for the conference proceedings, but one or two figures that were printed in black and white are color here. In addition, two technical reports are avaliable, Image-Based BRDF Measurement and Reflectance Measurements of Human Skin. These provide added technical detail.



Overview of gonioreflectometer

Hongsong Li, Sing-Choong Foo, Kenneth E. Torrance, and Stephen H. Westin.
Automated three-axis gonioreflectometer for computer graphics applications.
Advanced Characterization Techniques for Optics, Semiconductors, and Nanotechnologies II, Proc. SPIE 5878, Aug. 2005.

Padauk: diffuse vs. new model

Stephen R. Marschner, Stephen H. Westin, Adam Arbree, and Jonathan T. Moon.
Measuring and Modeling the Appearance of Finished Wood.
ACM Transactions on Graphics, Proceedings of SIGGRAPH 2005.

Rendering of automotive shape

James A. Ferwerda, Stephen H. Westin, Randall C. Smith, and Richard Pawlicki.
Effects of rendering on shape perception in automobile design.
First ACM Symposium on Applied Perception in Graphics and Visualization, July 2004, 107-114.

Setup for camera measurement

Stephen R. Marschner, Stephen H. Westin, Eric P. F. Lafortune, and Kenneth E. Torrance.
Image-based bidirectional reflectance distribution function measurement.
Applied Optics-OT, 39(16):2592--2600, June 2000.

Renderings from measured skin BRDF

Stephen R. Marschner, Stephen H. Westin, Eric P. F. Lafortune, Kenneth E. Torrance, and Donald P. Greenberg.
Image-based brdf measurement including human skin.
In Eurographics Workshop on Rendering, 1999.

This is a PDF file distilled from the actual PostScript® file submitted for the conference proceedings, but one or two figures that were printed in black and white are color here.

Brushed aluminum wheel

Stephen H. Westin, James R. Arvo, and Kenneth E. Torrance.
Predicting reflectance functions from complex surfaces.
Computer Graphics (SIGGRAPH '92 Proceedings), 26:255--264, July 1992.

This is a modified version of the PostScript® file used to make the camera-ready copy. I had to insert the images by hand, so cropping and alignment may be a bit different from the SIGGRAPH proceedings. Microgeometry for various surfaces and images used in the paper are also available.

Kitchen with non-Lambertian surfaces

François X. Sillion, James R. Arvo, Stephen H. Westin, and Donald P. Greenberg.
A global illumination solution for general reflectance distributions.
Computer Graphics (SIGGRAPH '91 Proceedings), 25:187--196, July 1991.

Technical reports

BRDF plots

Stephen H. Westin, Hongsong Li, and Kenneth E. Torrance.
A comparison of four brdf models.
Technical report PCG-04-02, Program of Computer Graphics, Cornell University, April 2004.

Two BRDF models for paper

Stephen H. Westin, Hongsong Li, and Kenneth E. Torrance.
A field guide to brdf models.
Technical report PCG-04-01, Program of Computer Graphics, Cornell University, Jan 2004.

Setup diagram

Stephen R. Marschner, Eric P. F. Lafortune, Stephen H. Westin, , Kenneth E. Torrance, and Donald P. Greenberg.
Image-based brdf measurement.
Technical report PCG-99-1, Program of Computer Graphics, Cornell University, Jan 1999.

Setup diagram

Stephen R. Marschner, Stephen H. Westin, Eric P. F. Lafortune, Kenneth E. Torrance, and Donald P. Greenberg.
Reflectance measurements of human skin.
Technical report PCG-99-2, Program of Computer Graphics, Cornell University, Jan 1999.

Master's Thesis

Full text of thesis (gzipped PostScript®) This file is about 1.8MB and contains all the figures. The images are all linear in intensity (i.e. no gamma correction).

Educational Material:


BRDF graph

K. E. Torrance and E. M. Sparrow.
Theory for Off-Specular Reflection from Rough Surfaces.
Journal of the Optical Society of America, vol. 57, no. 9, pp. 1105-1114, 1967.
I scanned this into a PDF file (0.9MB).

He-Torrance BRDF Implementation

HeTorrance graph

Xiao D. He, Kenneth E. Torrance, Francois X. Sillion, and Donald P. Greenberg.
A comprehensive physical model for light reflection.
Computer Graphics (SIGGRAPH '91 Proceedings), 25(4):175--186, July 1991.
Liang Peng and I implemented the model in C++ and verified against the original C implementation of the 1991 paper.

Fresnel Reflectance

Black glass sphere

About Fresnel Reflectance, a short sermon on what it is and why you probably want to use it.

Gamma Correction

Gamma curve

I have written a brief practical explanation of monitor gamma correction, including how to find out the correction for your display.

Multimedia Paper

Albedo graph

Try the developing version of the SIGGRAPH '92 multimedia paper, A Fast and Accurate Light Reflection Model. This is eventually intended to be a complete translation into HTML and Java of the NeXT-based MediaView document. The interactive Java illustrations basically work, but lack some of the functionality present on the NeXT. There is also one animation that we haven't managed to resurrect.


Albedo graph

I have translated the paper Ein Beitrag zur Optik der Farbanstriche, by Paul Kubelka and Franz Munk, in Zeitschrift für Technishen Physik 12(112). Get the gzipped PostScript® file or the Acrobat PDF file. The PostScript® is about 144K bytes compressed, 588K bytes uncompressed; the PDF file is about 118K. This translation is gradually improving; please send me your corrections and suggestions. Updated Friday, March 12, 2004.

Since posting this translation on the Web, I was contacted by Paul Kubelka’s son Werner, who lives in Brazil. He graciously sent me an autobiographical sketch that his father wrote, apparently in the 1940s.

Lafortune BRDF Representation

Two spheres from 1997 paper

I have written a simple RenderMan shader to implement the BRDF representation presented in Non-linear approximation of reflectance functions, by Lafortune et al. at SIGGRAPH 97. A sample RIB file showing its application to modeling human skin from measured data, compared with Matt Pharr's quick hack, is here. The resulting image from BMRT is here.

Other stuff

Lens register list


Willem-Jan Markerink has compiled an extensive list of registers (flange-to-film distances) for many cameras. I have made a nicely-formatted version of his list, with some additions and corrections. I also have sorted the list by flange distance to make it easier to see which adaptations might be feasible.

Camera resolution test chart

ISO chart

The International Standards Organization has adopted ISO Standard 12233: Photography -- Electronic still-picture cameras -- Resolution measurements for the measurement of camera resolution. The procedure requires a standard test target, which I have converted to a vector format so you can print your own.

Canon digital camera protocol


As part of the gphoto project, I have helped to update and expand the document describing the serial and USB protocol for communicating with Canon cameras. I provide a prebuilt HTML version of the document here as a convenience for those wha want to communicate with Canon cameras, but don't want to download the entire libgphoto2 source.

Sigma SA lens mount vs. Pentax K


Sigma SLR cameras use a unique lens mount that seems to be derived from the Pentax K bayonet mount. I have compared the two and offer a drawing with the results here. NOTE: this is an SVG document, so you may need to download a browser plugin to display it. The link to do so is on the page.

Windows Character Codes


After years of mystification of how to generate special characters in Windows NT, 200, and XP, I think I have learned something about Windows character codes.

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Stephen H. Westin <>
Last modified: Sun May 3 13:18:52 EDT 2015