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Ray diagram is the most viewed applet in our site and also the first applet that we have ported to Android (available on the market as free app)
Ultrastudio.org is a manually curated collection of educational Java applets, supplemented by the corresponding "encyclopedia-style" articles. Most of these visualizations were written on the raise of applets and Java programming language. Frequently they were written by people highly competent in the subject being illustrated (biology, physics, higher mathematics) rather than in programming. Where the licensing permits (as a rule, must be open source), we collect, review and fix such applets from the whole web, as well as offering a collection of our own applets. Below, you will find the overview of that we have already done. Few applets only required to find them however programming effort was often necessary to revive them for a second life.

As the documentation is equally important, and many applets come without it, we also write short introductory articles on the subject. Expecting for some input from the community, we have made the most of pages user editable. If you add some major information, please cite the references so we could easier review your input. We use Creative Commons license so your contribution will not be bound to our project.

The category summaries below do not list all topics we have, and the the number of screen shots is this page is much less than the overall number of visualizations available. Instead, the goal of summary is to provide a brief topic overview and show some featured applets. To see the full list of relevant topics, click on the category title. Topics with no obvious classification may be placed into several categories.

All applets on this site have always been running as untrusted (unsigned). This means, they run in a sandbox with highly restricted rights, without access to your hard drive or anything the like. However it may be more important that we have seriously looked into source code of every applet we show here. Starting from Java 7 update 51, now Oracle Java virtual machine blocks unsigned applets by default, while they have been running on a web since Java first came on. This essentially disabled the site for the end user who just wants to read articles and view animations. However we decided not to shut down the site as applet descriptions and they open source code still may be interesting for developers. We are also slowly migrating them to Android one by one, making part of the F-Droid project

You can always submit a new applet (source code only) but surely it will not run before we carefully review your code and upload the signed version.

Contents of this page:

Astronomy, geography

We have real time ("how it looks now") views of Mars globe, Moon phase, night sky view with both stars and planets included as well as real time positions of satellites around Saturn and Jupiter. Part of this collection, known as "akklets" (by the name of the author) was initially written for Sharp Zaurus and required some porting. There are also less flashy but also interesting form-based applets to compute sunrise and sunset times and to convert between the Earth coordinate systems.


Fifteen different types of barcode can be generated online directly from your input, from classic Codabar till PDF417 and DataMatrix. Most, but not all codes have dedicated articles but you can always switch the single used applet to show any barcode. This visualization set is derived from the single Barcode4J project that once received Project Of the Month award in SourceForge.


Eleven articles provide an overview of the sequence alignment algorithms and include both introductory topics (local and global alignment, gap penalty, dynamic programming table, suffix tree, etc) and algorithms in practical use like Smith & Waterman search. Visualizations allow to specify sequence or sequences used in demonstrations, answering that way various "what if" questions. Where relevant, they allow step by step execution. Collection includes classic "must to have" applets like reverse complement and RNA to protein translation.


Some of the most complex and advanced applets in biology section have seen the Nature pages in the past and many are written by competent researchers.

We present several topics on electrophysiology that were written by professionals and once released under GPL. Visualizations on morphogenesis and plant orientation were also written to supplement scientific papers in the past. The flock visualizer reliably shows that a group of individuals may have very coordinated activity without having any leader. Biomorphs illustrate some hypothesis on how the evolution may happen.


Due recent contribution we also have a good introductory series about complex plane and also Besicovitch set and Penrose map from the same source. The interactive demonstration of image processing (2D FFT) is available. On SourceForge we found a nice WMC framework to create visualizations of the simple curves with very little programming, but due us being busy with other parts of the project only parabola and logistic growth have been implemented. Generalized Lambda distribution is our first "extinct" applet that ceased to exist anywhere apart our site. The first applet of our project, Mandelbrot set (kind of something "must to have"), was also a mathematical applet.

Mathematical section also contains a "mystery visualization" of the fundamental domain - the only applet for that we were not able to write any article as did not manage to understand that it is showing. Maybe you could help?


The digital electronics series is based on the extended derivative of the SimCir project that (unlike original version) also includes the delay element. This element allows to demonstrate the work of T and JK flip-flops as well as problems that simple adder has and a look-ahead adder solves. A number of logic gates is covered, from classic AND or XOR till less known but also important C and Toffoli. The total number of available visualizations for various digital circuits is about 25, frequently more than one per article.

Analog electronics include quite important Poles and Zeros topic about analog filtering of the signal, and how to compute such filters with desired parameters. The collection also contains a single cascade transistor amplifier circuit that allows user to alter many parameters and shows the simulated currents and voltages. Depending on how resistors are set, it can demonstrate the work of both grounded collector and grounded emitter.


We are surely not a gaming site but do have several pages that could be classified as games. A good example of the "game we would like to have" is the Disjoint squares game. Despite of relatively simple rules, this game has been created by professor and reflects some fundamental tasks of combinatorial geometry.

In Conway's Game of Life series a single applet shows evolution of various colonies, depending on parameters. The user can pause, step and add or remove cells at any step of evolution. Rubik's cube is a working example of 3D visualization even without any graphic acceleration and could also be configured to show up differently. There is a very comprehensive applet on Sudoku, while seems not very popular for some reason. Dissociated press is just a part of the whole hacker culture. There are also two variations of Tic tac toe.


Physics section contains 15 topics, and unlike with barcodes and digital circuits, visualizations here are mostly independent, each being a result of independent work, frequently by different author. Ray diagram that we initially took from SourceForge but extended in a number of ways seems the most popular applet in all project. From optics, we also have our own Prism. Also Wikipedia uses a screen shot of our Atomic orbitals visualization that we have contributed there. This group also contains pendulum, the only finished visualization of Labs4Wikiversity, the first active project to use applets systematically in encyclopedic material. We have found unusually well prepared open source visualization and explanation of two dimensional collision. Rutherford scattering, while easy enough to understand, can be very nicely illustrated with the applet. Differently, wave packets brings us into the true physical jungles of the wave particle dualism. Brownian motion, while easy enough to understand without visualization, offers interesting experiments due its "time machine". There are also many less popular but also interesting topics in this category.


We visualize some of the most important algorithms that make the base of many programs. The core Quicksort was likely written on the dawn of Java by Sun Microsystems itself (we wrote a presentation part). Hashtable is a simple and clear demo how this structure works, and allow to experiment with various "what if" cases. The graph/tree applet (our own) visualizes many important graph search, from A* till Dijkstra, making the base of multiple articles that briefly introduce these algorithms. The visualization on how to find the two closest points in linear time has many practical applications. 2-3-4 tree allows to insert and delete user-given values, step by step if preferred. Lisp interpreter allows to get quickly the basic ideas of this great language. RSA is explained.

Near 30 topics can be directly or indirectly assigned to this category, too many for talking about them all in the front page. Please visit the category page to see them all.


<a href="/en/Matrix" title="Matrix">Matrix</a> operations
Matrix operations
Finally, there is a group that apart illustrating the topic can also be used to calculate something you may actually need. regular expressions applet allows to test easily the work of Java regular expression. There is a calculator for matrix operations and also the ordinary calculator. Our base converter can convert between any two bases and also converts the fractional part.
Base converter seems the most directly useful applet


Our last category contains visualizations of topics so complex that it is not possible for us to write a proper introductory material. Instead, we can only give references to the literature, trying to pick something that is more easy to read. We still add some extensions to these applets, such as mouse wheel support or some very technical bug fixes.

You can just play with applets from this mystery collection, as children do with mandelbrot set. This last group is the attic of the project, and we do not expect to have a lot of visualizations there.