VRML - A new tool in biomedical education
Director, Center for Scientific Visualization
Faculty for Electrotechnics, University Ljubljana
Trzaska 25, SLO-1000 Ljubljana, Slovenia
VRML (Virtual Reality Modelling Language) represents a fully interactive multimedia learning environment in the virtual 3D space. It has a unique advantage that its files are about 100x smaller in size than the corresponding video clips. This software is free, platform independent and can be observed with a web browser. By applying this technology many educational projects do not need to be distributed on CD ROMs anymore. Because of their small file size (typically about 3 MB) they can be downloaded from the web.
We use VRML to show the structures and functions of biological systems for the educational purposes in the secondary and high schools. Such three-dimensional worlds allow the user to travel in their virtual space, learning the principles of biological systems in a fast, effective and pleasant way. Therefore we believe that this technique will play in future a role in biological publications as important as today are the illustrations added to text.
Many of our creations can be observed on our web page http://verbena.fe.uni-lj.si/~tomaz/VRML/
A short description of the tool
A VRML (Virtual Reality Modelling Language) world is a readable text file containing descriptions of a virtual three-dimensional (3D) world. You can start making such a world by simply writing the VRML text file, but a faster way is to use one of the authoring tools which enable you to create a simple scene in minutes from scratch and without previous knowledge. You then observe your creation with a VRML browser (Netscape) with plugin for VRML which you obtain for free. New Netscape editions have this facility already installed. VRML world opens to you through a window which has in its lower part a dashboard with controls for moving around in the 3D space. You can observe objects from any side or angle you want to. However, this often leads to confusion and you get "lost in space". Therefore 'viewpoints' are provided which establish a safe guided path. I associate them with fish icons pointing like arrows into appropriate directions. A mouse click on a fish and you arrive to the next viewpoint. The objects can be animated and sound or video clips can be added. As just mentioned, some objects can be made "hot" - click on them and you start some animation or you get transported to another scene or another web document anywhere on the world. If you construct your VRML world with care, you obtain a file so small in size that you can use it embedded in your web page. The elements that make VRML files large are long sound or video clips and complex objects. This does not mean that you can't afford to show complex biological structures with VRML. You only have to split the complex scene into many smaller components, so that the user doesn't get a single large file at a time. It is the simple and effective strategy for web documents: give a huge amount of information, but download only a drop of it at a time.
How to use this tool in biological systems
VRML produces objects with planar faces and sharp edges - nice for some architectural project, but unsuitable for biological structures with curved faces and complex structures. Of course it is possible to build very complex structures with VRML, but the result is also a large data file on disk which is slowly transmitted on the web and renders slow on an average PC. The answer to this problem is polygon reduction. You reduce the number of planar faces the object is composed of at the same time observing how it looks with less polygons. When you produce an object which still shows the important morphological features of its original, but smaller than 100KB in file size, then you reached the goal. The next set of problems contains the sound and video clips. These files are also large and have to be used with caution. It is a good advice to use short sound clips. Repeating them while varying their pitch produces a simple synthesizer. One has to compose a VRML based story of many VRML worlds connected by links. At the beginning the animation shows only the most important outlines of the biological structures and functions under discussion. It shows also in user-friendly way how to proceed further to animations showing more details. It has become our tradition to use fish icons as pointers to further viewpoints or scenes. We also embed VRML worlds in standard HTML documents with additional information like illustrated text. So one gets an overall complete picture of a biological system from many VRML and HTML documents. The philosophy is identical to the internet praxis as already described above - from a huge amount of information on the web you get only a drop at a time.
VRML is still being developed
The main drawback of VRML is that its plugin is not yet widely distributed. Many people that encounter a VRML visualization don't have a VRML plugin on their platform and don't take the time to install it. So they can't see the VRML world at all and are not impressed by it. VRML is platform independent, which means that it runs on all computers similar to the Java programs. But there is a large difference in quality of VRML plug ins. At the moment of writing this text the PC platform has the best VRML plugin (Cosmo Player 2.1 which was originally developed by Silicon Graphics). A good, but recently not updated plugin exists for Unix (Cosmo Player 1.1). Those working on Macintosh platforms often report having problems with installing the VRML plugin for the Mac. To make the matter worse, Internet Explorer does not support VRML as good as Netscape and both browsers often crash with some VRML worlds. So the user might even become afraid of opening a VRML document because he can then lose also other browser windows he has already opened. Fixing these problems is the task of big companies like Platinum, the most important company producing VRML authoring and viewing tools at the moment. It is expected that in the near future the problems with VRML standardization will be over and VRML worlds will be integrated into the web documents as seamlessly as a Java applet today. When this happens, and it can be very soon, the VRML authors should already have their applications ready for the distribution.
Living structures are three-dimensional objects living in 3D space. So
it is naturally to learn about them in 3D space. Everybody is familiar with models
of human organs of gypsum or plastic from the school. Now it is
possible to establish similar virtual models which can be manipulated
by individuals on their computer. The users of virtual models cannot physically touch them as they can touch "real" models, but
instead they get many computer simulations about the function of the
organs depicted by the models. If one adds such functions to plastic
models, they become very expensive. The VRML visualization is much
cheaper, because it is "only" computer programming and
producing new copies is trivial. Some simulations can be better
performed in real world with real experiments like examining the
optical properties of the eye lens. On the other hand the computer
animation is more appropriate for studying the excitation of the eye
retina where light invokes changes of the electrical potential in the
receptor and nerve cells. In other words, it is better to perform real
experiments where this is possible. But often experimenting would take
too much time and money or would be dangerous etc. Here computer
simulations become important as the preparation to the real experiment.
For example, surgeons study 3D computer visualizations of patient's
organs before they start with operation: