
Computer Science
Program  Emeritus
Address:
Personal Profile:

Traditional Courses of Mine:
B581, Graduate Computer Graphics.
Public B581 syllabus: Overview of B581.
This was an OpenGLbased course introducing the mathematical foundations and practical programming methods of modern interactive computer graphics. The homework involves coding in C using OpenGL and GLUT, and mastering the theoretical principles upon which OpenGLlike graphics is based. The course emphasized creating interactive interfaces to help understand the graphics objects and techniques being studied. Lighting and simple material modeling were covered as an introduction to the creation of realistic images.
B689, Mathematical Modeling Methods for Scientific Visualization.
Public B689 syllabus: Overview of B689.This course focused on Mathematicabased methods of producing rapid prototypes solving complex software modeling problems. This class introduced the Mathematica programming environment, and incorporated Mathematica prototyping methods implicitly into a broad survey of mathematical modeling methods, techniques, and folklore used widely throughout computer science, computer graphics, scientific visualization, mathematics, and physics.
Current Research
My most recent research focuses on several areas: Mathematical Physics, Applications of Quaternions, Human Interfaces for Effective Learning, and Scientific Visualization.
Quaternion Rotations  
This WebGL App (implemented by Leif Christiansen from a corresponding OpenGL desktop application) uses the leftmouse (or 1finger) drag to apply a 3D rotation to a triad of axes, each corresponding to a column of a 3D rotation matrix. As the rotations accumulate, the lefthand bar shows the corresponding quaternion q_{0} component, and the thick tube emanating from the origin shows the (q_{x},q_{y},q_{z}) 3vector component. If q_{0}≥0, the components show in yellow, and if q_{0}<0, the components show in blue. The entire viewpoint can be rotated without changing the matrix or its quaternion components using mouseright, and altleftmouse restricts the rotation to the zaxis for pedagogical study. The application is here: The QuatRot App. 
4D Objects with 3D and 4D Rotations
This WebGL App (implemented by Leif Christiansen from a corresponding OpenGL desktop application) uses the leftmouse (or 1finger) drag to apply a 3D rotation to any chosen projection of a 4D object. On the desktop, shiftmouseleft rotates in the 4D zw plane, and altmouseleft uses both up/down and leftright mouse drags to rotate in the combined xw and zw directions. On a touchscreen device, check the boxes for fixed zaxis and xwplane and ywplane rotation to change from 1finger 3D rotation to the above 4D operations. Among the available shapes are a 2torus manifold embedded in 4D, a 4D Veronese embedding of Steiner's Roman Surface (the 2D projective plane), and a variety of Fermat surfaces in CP^{2} labeled as CalabiYau manifolds, with N=5 being the 2D crosssection of the 6manifold that is a candidate for the hidden dimensions of 10dimensional string theory. The application is here: The 4D Object Exploration App 
4Dice is my (free) iPhone App first posted in 2012. 4DRoom, first posted in 2017, is an extension of the 4Dice context to the interior of a 4dimensional room, including a virtualreality mode that rotates in the 4D wx plane as you rotate your body with your iPhone. (More details below.) 
Images of the CalabiYau Quintic: Hidden dimensions of string theory 
Shown below are my graphical representations of the
CalabiYau quintic representing the hidden dimensions of string
theory, based
on my 1994 paper. These were made available on the
Wiki Commons domain in 2014, and clicking on the images takes you to
the source material. The first is a 2dimensional crosssection of
the quintic in CP^{2}, and the second is a complete
6dimensional representation of the (local C^{4}) quintic
embedded in CP^{4} using 4D discrete samples in a
C^{2} subspace to produce a hypercubic array of the
corresponding varying 2D crosssections. 
The QuaternionBased SpatialCoordinate and OrientationFrame Alignment Problems, by Andrew J. Hanson. https://doi.org/10.1107/S2053273320002648: Acta Crystallographica A 76 (4), pp. 432457, July 2020. We are featured on the Cover Page of the July issue. We review the problem of transforming matching collections of data points into optimal correspondence. The classic RMSD (rootmeansquare deviation) method (sometimes referred to as the "Orthogonal Procrustes Problem,") calculates a 3D rotation that minimizes the RMSD of a set of 3D test data points relative to a reference set of corresponding points. Similar literature threads in proteomics, aeronautics, photogrammetry, and digital heritage employ an approach based on the maximal eigenvalue of a particular 4x4 quaternionbased matrix, thus specifying the quaternion eigenvector corresponding to the optimal 3D rotation. Much of the literature uses numerical methods to solve this eigenvalue problem; we also explore the features of algebraic solutions based on the 16th century solutions of the quartic equation. In addition, we show how these methods can be extended to include 3D orientationframe matching using quaternion frame representations. Further extensions of the quaternion method are given for 4D spatialcoordinate and 4D orientationframe data sets. (An earlier obsolete version appears on the arXiv, http://arxiv.org/abs/1804.03528.) 
[DQT3] Quantum IntervalValued Probability: Contextuality and the Born Rule, by YuTsung Tai, Andrew J. Hanson, Gerardo Ortiz, and Amr Sabry, (Physical Review A, 97, (5), 1 May 2018). DOI: 10.1103/PhysRevA.97.052121. We present a mathematical framework based on quantum intervalvalued probability measures to study the effect of experimental imperfections and finite precision mesasurements on defining aspects of quantum mechanics such as contextuality and the Born rule. This work continues our systematic investigation into finite precision, limited resources, and errorful processes in quantum mechanics. A preprint is posted on the arXiv: https://arxiv.org/abs/1712.09006. 
Isometric Embedding of the A_{1} Gravitational Instanton, by Andrew J. Hanson and JiPing Sha, pp. 95111, appearing in "Memorial Volume for Kerson Huang, " Ed. K.K. Phua, H.B.Low, & C. Xiong, World Scientific Pub. Co., Singapore (2017). ISBN13: 9789813207424, ISBN10: 9813207426, available here. A local copy can be found here. 
Memories of Kerson Huang, by Andrew J. Hanson, pp. 1316, appearing in "Memorial Volume for Kerson Huang, " Ed. K.K. Phua, H.B.Low, & C. Xiong, World Scientific Pub. Co., Singapore (2017). ISBN13: 9789813207424, ISBN10: 9813207426, available here. A local copy can be found here. 
Charting the Interstellar Magnetic Field behind the Interstellar Boundary Explorer (IBEX) Ribbon of Energetic Neutral Atoms, by P.C. Frisch, A. Berdyugin, V. Piirola, A.M. Magalhaes, D.B. Seriacopi, S.J. Wiktorowicz, BG Andersson, H.O. Funsten, D.J. McComas, N.A. Schwadron, J.D. Slavin, A.J. Hanson, and C.W. Fu, appearing in Astrophysical Journal, November, 2015. A local copy can be found here. 
[DQT2] Discrete Quantum Theories, by Andrew J. Hanson, Gerardo Ortiz, Amr Sabry, and YuTsung Tai, appearing in J. Phys. A: Math. Theor. 47 (2014) 115305 (20pp) (March, 2014). This work continues a systematic investigation of the formulation of discrete quantum computing using finite fields, and introduces that concept of Cardinal Probability as a way of dealing with probabilistic concepts in the absence of ordered numbers for finite fields. The DOI link is doi:10.1088/17518113/47/11/115305. A local copy can be found here. 
[DQT1] Geometry of Discrete Quantum Computing, by Andrew J. Hanson, Gerardo Ortiz, Amr Sabry, and YuTsung Tai, appearing in J. Phys. A: Math. Theor. 46, no. 18, pp. 185301 (22 pages), (2013). The DOI link is doi:10.1088/17518113/46/18/185301, This work presents the mathematical elements of the consequences of formulating quantum computation and qubits in terms of discrete, computable numbers, using complexifiable fields with finite characteristic. A local copy can be found here. 
Scheduling Scaffolding: The Extent and Arrangement of Assistance During Training Impacts Test Performance, by Jonathan G. Tullis, Robert L. Goldstone, and Andrew J. Hanson, appearing in the Journal of Motor Behavior, pp 0111, (2015) The DOI is DOI:10.1080/00222895.2015.1008686. 
Putting Science First: Distinguishing Visualizations from Pretty Pictures. Andrew J. Hanson, "Putting Science First: Distinguishing Visualizations from Pretty Pictures," in Visualization Viewpoints column, TheresaMarie Rhyne, editor. IEEE Computer Graphics and Applications, Vol 34, No. 4, pages 6369, (July/August 2014). A local copy is here. 
Interactive Exploration of 4D Geometry with Volumetric Halos Weiming Wang, Xiaoqi Yan, ChiWing Fu, Andrew J. Hanson, and PhengAnn Heng. ``Interactive Exploration of 4D Geometry with Volumetric Halos.'' In Proceedings of Pacific Graphics 2013 (Singapore, October 79, 2013). The DOI link is DOI:10.2312/PE.PG.PG2013short.001006. A local copy is here. 
Multitouching the Fourth Dimension. By Xiaoqi Yan, ChiWing Fu, and Andrew J. Hanson, IEEE Computer, Volume 45, Number 9, pp.8088 (September, 2012). The IEEE site for the article is here, and a local copy can be found here. 
Localization of polymerase IV in Escherichia coli By Sarita Mallik, Ellen M. Popodi, Andrew J. Hanson, and Patricia L. Foster. "Interactions and localization of Escherichia coli errorprone DNA polymerase IV after DNA damage," J. Bacteriol. (June 2015). Accepted manuscript posted online 22 June 2015. DOI link is here doi:10.1128/JB.0010115, Abstract is here, and the prepublication manuscript is here. 
Mutational Topology of the Bacterial Genome. By Patricia L. Foster, Andrew J. Hanson, Heewook Lee, Ellen Popodi, and Haixu Tang. "On the Mutational Topology of the Bacterial Genome," G3: Genes, Genomes, Genetics, Volume 3, no. 3, pp. 399407 (March 2013). Pub Med link: is here, DOI link is here, and the Journal URL link is here. 
"Quaternion maps of global protein structure," By A.J. Hanson and S. Thakur, appearing in Journal of Molecular Graphics and Modelling, Volume 38, September 2012, pp. 256278. The paper PDF site is here, and a local copy can be found here. 
Talk canceled by SARSCoV2 Pandemic. Visualizing the EguchiHanson Space, Andrew J. Hanson. I was scheduled to give a talk entitled "Visualizing the EguchiHanson Space" on 14 March 2020 at the Komaba Campus of the University of Tokyo as part of a memorial celebration in honor of my collaborator Tohru Eguchi, who passed away on 30 January 2019 at the tooyoung age of 70. Unfortunately, the events were canceled a week before I was scheduled to fly to Japan due to concerns with the rapidly spreading Coronavirus epidemic. The planned talk contains a mixture of topics aimed at both honoring Eguchisan and exposing a mixed audience of younger and older, mathematicians and physicists, to the work Eguchi and I did together. The technical portion of the talk is based on the paper Isometric Embedding of the A_{1} Gravitational Instanton, by Andrew J. Hanson and JiPing Sha, appearing in "Memorial Volume for Kerson Huang, " World Sci Pub., Singapore (2017), pp. 95111, linked here. 
Talk. Illustrating String Theory Using Fermat Surfaces, Andrew J. Hanson, "Illustrating String Theory Using Fermat Surfaces," 19 September, 2019. ICERM workshop "Illustrating Geometry and Topology," Brown University, 1620 September, 2019. Exploring the path leading from attempts to visualize Fermat's "Last Theorem," via superquadrics, to illustrations of the CalabiYau quintic representing the hidden dimensions of String Theory. 
Talk. Matching Paired Sets of Space Space and Orientation Data, Andrew J. Hanson ``Matching Paired Sets of Space and Orientation Data,'' 17 October, 2018. Wolfram Technology Conference 2018 (1619 October 2018, Champaign, Illinois). 
Talk. Matching Stuff with Quaternions and Hough, Andrew J. Hanson ``Matching Stuff with Quaternions and Hough,'' 22 June, 2018. ASIC 2018 (1722 June 2018, Loano 3 Village, Italy). 
Talk. The 4D Room, Andrew J. Hanson ``The 4D Room,'' 20 July, 2017. ASIC 2017 (1520 July 2017, Interlaken, Switzerland). 
Talk. Discrete Quantum Computing, Andrew J. Hanson (with Gerardo Ortiz, Amr Sabry, and YuTsung Tai), Seminar for Quantum Computing Group, Computer Science, Oxford University, Oxford, UK (25 July, 2014). 
Talk. The Bugcatcher. Andrew J. Hanson (with Jonathan Tullis and Rob Goldstone), ``The Bugcatcher,'' 25 June, 2014. ASIC 2014 (2327 June 2014, Moab, Utah). 
Talk. Multitouching the Fourth Dimension. Andrew J. Hanson, ``Multitouching the Fourth Dimension,'' ASIC 2013 (2430 July 2013, Cortina d'Ampezzo, Italy). 
Course. Quaternion Applications. Andrew J. Hanson: Presented at Siggraph Asia (Singapore, 29 November, 2012). New application topics included optimal, smoothly controllable tubing and tube texturing, quaternion protein maps, and how dual quaternions solve the centuryold conundrum of how a quaternion acts on a vector. 

Click here for a larger version 
4Dice is my (free) iPhone App first posted in 2012.
4DRoom, first posted in 2017, is an extension of
the 4Dice context to the interior of a 4dimensional
room, including a virtualreality mode that rotates in the
4D wx plane as you rotate your body with your iPhone.
( 4D Client, first posted in 2016, is an unsupported iPhonebased utility system that implements the 4D Multitouch controls of the 4Dice design to control a desktop 4D application over the internet. Example code for an elementary interface is available in "iPodLink.cpp" linked in the 4Dice web repository. This application is used for our internal research purposes; we do not have the resources to provide support for outside users, though anyone is welcome to use it.) 
4Dice is an interactive application using our 4D Rolling Ball algorithm combined with the graphically correct 4D backfaceculled representation of the hypercube introduced in the 4Dice video animation (see below). This is a collaborative project with Xiaoqi Yan, originally at NTU Singapore, and Prof. Philip ChiWing Fu, now at CUHK, Hong Kong. The extension of 4Dice to handle the context of the 4DRoom was implemented principally by Leif Christiansen at Indiana University.
For the mathematical details of the 4D control design of 4Dice, see our IEEE COMPUTER paper (pdf link: here.) IEEE Computer, Volume 45, Number 9, pp.8088 (September, 2012). Alternative site for PDF: see also here.
The 4Dice oneminute YouTube video from 1995 provides a quick introduction to the issues of properly visualizing a backface culled hypercube; the 4Dice iPhone App provides interactive exploration of all the concepts introduced in this animation.
QuatRot and 4DTemplate are draft interactive applications by Leif Christiansen using WebGL. See (QuatRot WebGL) and (4DTemplate WebGL.)





 
The images you see in the 4Dice interactive application
actually form a wireframe torus when you turn off backface
culling. The deep reason for this is that the hypercube is a simple
tessellation of a 3sphere (which has Euler characteristic zero)
surrounding a 4ball, and a nice parameterization of the 3sphere
involves a nested family of tori; the wireframe hypercube is
effectively a rectangular tessellation of the "center"
member of this family of tori. It is known that such a set of
edges, with four edges meeting at each vertex, admits
an Eulerian
path. The figure on the left shows one of many such paths
that can be constructed, with a ratio of 
Selected Publications of Interest
Visualizing Quaternions
(MorganKaufmann/Elsevier, 2006, ISBN 9780120884001)
is a comprehensive approach to the
significance and applications of quaternions,
and focuses on the exploitation of Quaternion Fields,
a tool developed primarily by the author.
The official website for the book is maintained by the publisher, and provides background material, downloadable material from tables, and demonstration software. I maintain a local companion website here, which may be more up to date. Updates and Errata: The known errata except for Chapter 29 have been corrected in the Elsevier eBook as of 2017. As of mid2018, the Amazon printondemand hardcopies have included (without any copyright page annotation) corrections of the coding typos and the new Chapter 29, but for some unknown reason, only about half of the typos corrected in the eBook made it into printondemand. As of spring 2020, we approached Elsevier once again to try to reconcile this bizarre situation, which is entirely beyond the author's control: I provided all the typo corrections to the publisher long ago. If you have an older print book or eBook, you just need to look at the list of known corrections that is maintained on my personal update and errata page, supplemented by the revised Ch. 29 pdf file. If you have a hardcopy book, and there is no line at the bottom of the copyright page that reads "This book is moved to digital printing, with reprint corrections, 2016. ", you cannot know if you have the older hardcopy with no corrections, or the newer one with only part of the corrections, including fixed transposed indices in Table E.3, page 446, and fixed matrix components for Chapter 29. If you have an eBook with that notation at the bottom of the copyright page, you have everything except Chapter 29. We are working with the publisher to get all media incorporating the known corrections, and with a " with reprint corrections, 2020 " notation added to all such corrected media. Addition: An example of something I should have
included in the book is the closed form doublereflection quaternion
form
 

Winner with coauthor Sidharth Thakur of the
2012 JMGM Graphics Prize.
See also the
MGMS/Elsevier Graphics Award. Quaternion maps of protein amino acid residues provide an alternative to Ramachandran plots for orientation analysis. Several alternative orientation frame systems can be chosen, with the residuelocal C_{α}centered frame being the default. Quaternion maps are noteworthy for their ability to compare the orientations of arbitrary sets of sequential or nonsequential residues located anywhere on the protein, and for the resulting opportunity to observe and analyze the statistical properties of global orientation clusters. Only the quaternion representation of orientation frames embodies a natural rigorous measure for comparing properties of sets of global orientation frames. 
Quaternion Applications were covered in our updated quaternion tutorial lectures presented at Siggraph Asia 2012, 29 November in Singapore. Special application topics included optimal, smoothly controllable tubing and tube texturing, quaternion protein maps, and how dual quaternions solve the conundrum of how a quaternion acts on a vector. The latter is a longstanding controversy that pitted Hamilton against many contemporaries, and has been described in wondrous detail by Altmann in "Hamilton, Rodrigues, and the Quaternion Scandal." The solution is simply to replace Hamilton's impossible candidate for
a "Vector," the binary rotation quaternion Visualizing Relativity using complexified quaternions was part of the material covered by Andrew Hanson and Daniel Weiskopf in their Siggraph 2001 Course 15 Notes. The Solar Journey Movie is an educational computer animated film on the astronomy of the local neighborhood of the Earth and the Sun developed as part of our NASAsponsored research work. A DVD version containing the Solar Journey animation and supplementary science materials exists but is no longer marketed. 
Some day I'll put together an annotated bibliography, but for now see the Google Scholar and DBLP project links at the top of the web page. Here is a summary of my historically most highly cited work, and together with some media links.
The EguchiHanson metric (Physics Letters 74B, pp. 249251 (1978)) is a vacuum solution of the Euclidean Einstein equations that is the first known instance of an important class of metrics now commonly referred to as ALE or Asymptotically Locally Euclidean metrics. A comprehensive review of Euclidean Einstein metrics and the context of the EguchiHanson metric is given in our 1979 Annals of Physics review article. This work won the Second Prize in the 1979 Gravity Research Foundation Competition; see T. Eguchi and A.J.Hanson, "Gravitational Instantons," Journal of General Relativity and Gravitation, 11, pp. 315320 (1979).
Our comprehensive introduction to the ways in which the languages of the theoretical physics and mathematics communities became inseparably connected after a long history of going their separate ways is available in the 1980 Physics Reports article "Gravitation, Gauge Theories and Differential Geometry" by Eguchi, Gilkey, and Hanson.
Constrained Hamiltonian Systems, is a short book by Hanson, Regge,
and Teitelboim, originally published in 1976 by the Accademia
Nazionale dei Lincei (Contributi del Centro Linceo Interdisc. di
Scienze Matem. e loro Applic., No.22, Accademia Nazionale dei Lincei,
Rome, 135 pages (1976)). Actual print copies of this work are rare
and generally unavailable.
Media. The fourdimensional MeshView viewer is described in the Meshview tech note, and downloadable software is located HERE. Supported fully under Xwindows/Motif only. Precompiled for Linux, Macintosh, SUN SOLARIS, and SGI IRIX. Recently available: reduced functionality Windows XP version. The shortcuts work in the Windows version, but you need to look at the Linux version to see what they are.
Some Selected Research Topics
My research has focused on several areas of science, including: Mathematical Visualization, Virtual Reality, and Astronomy.
A Tessellation for Fermat Surfaces in CP^{3},
DOI link
10.1016/j.jsc.2008.09.002, appears in the Journal of Symbolic Computation
(Sept 2008). This work presents an explicit algorithm for tessellating
the algebraic surfaces (real 4manifolds) F(n) embedded in
CP^{3} defined
by the "Fermat" equation
 
Dual FivePoint Function Geometry.
This work investigates the geometry of twocomplexvariable
contour integration using the classic 1960's Dual 5Point Function of
the early string model as the critical example. The investigation
actually began with some questions introduced in a very early
paper, Dual NPoint Functions in
PGL(N2,C)Invariant Formalism (A. J. Hanson, Physical Review, 1972).
A number of new insights are given in our paper "A Contour Integral Representation for the Dual FivePoint Function and a Symmetry of the Genus Four Surface in R6" by Andrew J. Hanson and JiPing Sha, DOI link 10.1088/03054470/39/10/01, which is published in J. Phys. A: Mathematics and General., vol. 39, pages 25092537 (2006). There is also a version on the arXiv, mathph/0510064. A local copy can be found here. 
Other topics. Various longterm projects deal with techniques for modeling, depicting, and interacting with geometric structures of extreme complexity. Subject domains of interest range from mathematical objects in four dimensions to exploiting quaternions to represent orientation fields of geometric objects. Recent work concerns rephrasing some of the classical differential geometry of curves and surfaces directly in terms of quaternion fields; an application is the determination of optimal framings of curves and surfaces by minimizing appropriate energies of the quaternion frame fields ("quaternion Gauss maps") in the 3sphere.
An example of our work on star rendering embedded in the Solar Journey package may be found in this QuickTime movie depicting simulated stars, which compares favorably to real images such as Akira Fujii's Orion.
Selected papers of ours in this area:
Visualizing Multiwavelength Astrophysical Data, Hongwei Li, ChiWing Fu, and Andrew J. Hanson, TVCG, Nov/Dec 2008, 14, no. 6, pp. 15551562, Proceedings of IEEE Visualization 2008. Describes a unique interactive GPUdriven volumerendering paradigm tailored to the study of allsky multispectral astrophysical data. Paper web site. 
Visualizing LargeScale Uncertainty in Astrophysical Data, Hongwei Li, ChiWing Fu, Yinggang Li, and Andrew J. Hanson, TVCG, Nov/Dec 2007, 13, no. 6, pp. 15401647; Proceedings of IEEE Visualization 2007. Astrophysical data is characterized by a wide variety of uncertainties and error sources; this work provides a set of tools for examining and visualizing these features. Paper and web site. 
Scalable WIM: Effective Exploration in Largescale Astrophysical Environments, TVCG, Sept/Oct 2006, 12, pp. 10051011; Proceedings of IEEE Visualization 2006. Describes a WorldinMiniature interface design for astrophysical exploration whose development was led by Yinggang Li in my laboratory. Paper and web site. 
A Transparently Scalable Visualization Architecture for Exploring the Universe, TVCG, Jan/Feb 2007, is a full description of work done mainly by ChiWing Fu in my laboratory. This framework supports transparent interactive navigation across enormous scale ranges such as those naturally occurring in astronomy. Paper and web site. 
Architectures for Very Large Scale Visualization of Astrophysical Environments.
Our initial work on handling very large scales of spacetime
in interactive virtual reality environments is described in our paper, Very large
scale visualization methods for astrophysical data, which appears in
Proceedings of Joint EurographicsIEEE TVCG Symposium on Visualization,
May 2931, 2000, Amsterdam, the Netherlands. This paper is part of these
published proceedings: SpringerVerlag.
Our most extensive work, which appeared in TVCG in 2007, describes the maturation of the scaling framework developed in Philip ChiWing Fu's PhD thesis, and is entitled A Transparently Scalable Visualization Architecture for Exploring the Universe. For details, see the journal article DOI:10.1109/TVCG.2007.2, TVCG, January/February 2007, pp. 108121, vol. 13. More details are available on Philip Fu's "powersof10" web site. A local copy can be found here. 
The Sun's interaction with its environment. This image of the heliosphere, representing the interaction of the Solar wind with the surrounding interstellar material, is taken from our short film "Solar Journey;" an extended version of the film will be produced for public distribution on videotape and DVD during the coming year. The shapes depicted here utilize a theoretical model by Timur Linde from the University of Chicago. The image has appeared as the Astronomy Picture of the Day, APOD 2002 June 24, and was used as an illustration in a recent astronomy news article in Science Magazine, page 2005 of Vol. 300, 27 June 2003. (The image credit is very obscure, in tiny verticallyaligned print along the spine of page 2005.) 
Satellites in our Sky (GMT June 24th 2003 2:21pm). We have over a thousand satellites flying through the sky over our heads. This image is from a brief animation representing a user's interaction with our Earthday graphics program. The animation shows a large portion of these at a selected time, and then zooms in for a closeup of the International Space station (ISS). We can clearly see the ring structure of geostationary (deepspace) satellites rotating with the Earth, located 38,500km above the Earth's surface (about 6 times the radius of the Earth). The entire animation appeared as the Astronomy Picture of the Day on 14 July 2003. See APOD 2003 July 14. 
I have also created a variety of graphics images derived from the Fermat Equation (see below) that are relevant to the CalabiYau spaces that may lie at the smallest scales of the unseen dimensions in String Theory; these have appeared in Brian Greene's books, The Elegant Universe and The Fabric of the Cosmos,, and in the book by Callender and Huggins, Physics Meets Philosophy at the Planck Scale. The writhing purple shapes in the October/ November 2003 NOVA production Elegant Universe, as well as the cover of the November 2003 Scientific American, were derived from software models I supplied to the NOVA graphics providers.
These images show equivalent renderings of a 2D crosssection of the
6D manifold embedded in CP4 described in string theory calculations by the
homogeneous equation in five complex variables:
z_{0}^{5} + z_{1}^{5} +
z_{2}^{5} + z_{3}^{5} +
z_{4}^{5} = 0
The surface is computed by assuming that some pair of complex inhomogenous
variables, say z_{3}/z_{0} and z_{4}/z_{0}, are constant (thus defining
a 2manifold slice of the 6manifold), normalizing the resulting inhomogeneous
equations a second time, and plotting the solutions to
z_{1}^{5} + z_{2}^{5} = 1
The resulting surface is embedded in 4D and projected to 3D using Mathematica
(left image) and our own interactive MeshView 4D viewer (right image). If
you have
CosmoPlayer, you can also
interact with this VRML version
of the quintic CalabiYau crosssection. This method is now obsolete,
as the WebGL
"4D Explorer" App runs on more platforms and has
a complete 4D interactive interface.
In the righthand image, each point on the surface where five differentcolored patches come together is a fixed point of a complex phase transformation; the colors are weighted by the amount of the phase displacement in z1 (red) and in z2 (green) from the fundamental domain, which is drawn in blue and is partially visible in the background. Thus the fact that there are five regions fanning out from each fixed point clearly emphasizes the quintic nature of this surface.
For further information, see: A.J. Hanson. A construction for computer visualization of certain complex curves. Notices of the Amer. Math. Soc., 41(9):11561163, November/December 1994.
An interactive version is available at
the Wolfram Demonstrations Project CalabiYau
Space page, based on the Hanson paper cited above, with
assistance from Jeff Bryant. Most features of the latter
are now available on the WebGL
"4D Explorer" App, implemented by Leif
Christiansen, which runs on more
platforms and has a complete 4D interactive interface.
Arbitrary Genus Surfaces:
This image shows my computer graphics construction of a fourhole
torus described by an equation in complex twospace given by H. Blaine
Lawson, "Complete Minimal Surfaces in S^{3}," Ann. of Math. 92,
pp.~335374 (1970), with m = n = 2,
Im z_{1}^{(m + 1)} +  z_{2} ^{(mn)} Im z_{2}^{(n+1)}
= 0
and
z_{1}^{2} + z_{2}^{2} = 1
In general,
the genus is m*n, and this surface is not actually minimal in S^{3}
except for
m = n = 0 and m = n = 1.
Review article
Cover picture: IEEE Computer 27 (July 1994)
Mathematics and Physics Animations
We have produced a number of short video animations with mathematical and physical content. Some of my favorite projects are the following: