Java 3D - What does it promise

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Java 3D - What does it promise? What does it offer? What is missing?

Java 3D is an API which extends the Java platform with advanced capabilities for three-dimensional graphics. After eight months since the launching of the Java 3D 1.0 API Specification, Sun has made available early access Java 3D 1.1 implementation (Alpha) for JavaOne Developer Conference on March 24, 1998. (Beta version is already available.) What makes unique this API is the combination between Java power, high quality object oriented design and the number of target platforms: Java 3D will be layered over the widely spread low-level 3D APIs: OpenGL, Direct3D, QuickDraw3D.

What does it promise?

<<JAVA 3D introduces a new view model that takes Java's vision of "write once, run anywhere" and generalizes it to include display devices and six-degrees-of-freedom input peripherals such as head trackers. This "write once, view everywhere" nature of the new view model means that an application or applet written using the Java 3D view model can render images to a broad range of display devices, including standard computer displays, multiple-projection display rooms, and head-mounted displays, without modification of the scene graph. It also means that the same application, once again without modification, can render stereoscopic views and can take advantage of the input from a head tracker to control the rendered view.>> (Java 3D API Specification, Chapter 8, "View Model")

Another big promise is high performance. In the current implementation, Java 3D is mixing a lot of Java code with OpenGL calls. Many of the existent Windows machines emulate Direct3D and OpenGL with pure software drivers. In such a configuration Java 3D is very slow, so next implementations should contain much more native optimizations. It shouldn't be neglected that IDEs like SuperCede and Symantec Visual Café offers the option to build native code. Such a facility will be very appreciated by the Java developers of the applications using 3D graphics.

What does it offer?

When I started to learn about Java, one of my first applets was Browser 3D. Its engine was pure Java and was calling the methods of the java.awt.Graphics class to put flat shaded polygons on screen. By analyzing its performances, I understood it was almost hopeless to improve it with texture mapping or a lighting model because these would have implied the computing of the image pixel by pixel. Java 3D makes possible texture mapping and the use of light sources in Java applets.

The most tempting offer of Java 3D is being easy-to-use: <<Java 3D allows the programmer to think about geometric objects rather than about triangles-about the scene and its composition rather than about how to write the rendering code for efficiently displaying the scene.>> (Java 3D API Specification, Chapter 1, "Introduction to Java 3D") The programmer creates objects containing geometric data, attribute information and viewing information and he connects them to form a treelike structure called "scene graph." The Java 3D API specification doesn't include indications for visual building of 3D worlds, but it is expected that third-parties will create applications which will allow rapid development of Java 3D applets.

The structure of the scene graph is very flexible. Node and NodeComponent derive from the SceneGraphObject class. The instances of the subclasses of the Group and Leaf classes (which inherit from Node) will form the scene graph and will contain references to instances of the subclasses of NodeComponent. <<A leaf node's state is defined by the nodes in a direct path between the scene graph's root and the leaf. Because a leaf's graphics context only relies on a linear path between the root and that node, the Java 3D renderer can decide to traverse the scene graph in whatever order it wishes. It can traverse the scene graph from left to right and top to bottom, in level order from right to left, or even in parallel. The only exceptions to this rule are spatially bounded attributes such as lights and fog.>> (Java 3D API Specification, Chapter 2, "Scene Graph Basics") In addition the subgraphs can be shared and cloned.

The scene graph can contain nodes that define the behavior of the 3D objects. <<Simple behaviors can add surprisingly interesting effects to a scene graph. For example, one can animate a rigid object by using a Behavior node to repetitively modify the TransformGroup node that points to the object one wishes to animate. Alternatively, a Behavior node can track the current position of a mouse and modify portions of the scene graph in response.>> (Java 3D API Specification, Chapter 9, "Behaviors and Interpolators") The Interpolators are a subclass of the Behavior nodes. They offer a quick way to animate a scene. <<The Java 3D API provides interpolators for a number of functions: manipulating transforms within a TransformGroup, modifying the values of a Switch node, and modifying Material attributes such as color and transparency.>> (Java 3D API Specification, Chapter 9, "Behaviors and Interpolators") For example, if you want to give a continuos rotation to an object then you can use RotationInterpolator. The specialized, frequently used classes can decrease the size of the applets.

The Java 3D features don't stop here. It offers support for collision detection, picking and spatial sound. There are three rendering modes: immediate mode, retained mode, and compiled-retained mode, which can be even mixed.

From the user's perspective, Java 3D will make possible the mixing of the text with high quality 3D graphics in HTML pages. Besides 3D logos, the articles might contain animations which will make them more easy to understand. But Java 3D isn't only for applets. The CAD applications will integrate much better with the Internet and the multi-player games will have something to gain too.

If the performances will be good enough then the developers of the graphics applications will choose Java 3D for portability and low development cost.

What is missing?

Java 3D hasn't a file format. This is right. Let the applications define their own graphics file formats. However, imagine you work for a tool that allows the user to create Virtual Universes in a visual mode, using Java 3D of course. After he finishes to build the scene the tool will generate the source code for an applet. The user closes the application and goes home. Next day he decides a few changes in the 3D scene are necessary. If the tool doesn't offer persistency for Virtual Universes then the user must either start it all over again or modify the source code of the applet. I wouldn’t like to be in his place. Unfortunately, the classes of Java 3D aren't serializable, so you may not use a technique like that used by BeanBox. (BeanBox can serialize JavaBeans for later modifications of their interrelations, and generates source code for applets, which may be inserted in Web pages.) In a future version, the Java 3D classes might be serializable.

The success of a 3D API can be assured by the game market. Games like Quake use Binary Space Partitioning Trees and data structures like Potentially Visible Sets. For each leaf of the BSP-tree, a list of potentially visible leafs (a PVS) is precalculated. The PVSs are coded at bit-level and they use RLE compression. Java 3D doesn't offer any support for something like this, and traversing these data structures using Java code will be very slow. The same thing is true for Artificial Intelligence, which must be incorporated in Behavior nodes. Moreover, the large files that define the levels and the textures make the download of complex games very difficult. However, if somebody releases an API for games layered on top of Java 3D then creative people could make great things.

Java 3D is designed for real-time animations so it shouldn't be a surprise that there is no support for printing and off-screen rendering. These would be necessary especially for rendering of photo-realistic images, which is not the case.

Conclusion

Sun succeeded with Java 1.0 where many failed: AWT abstracted the APIs for User Interface of the widely used operating systems. With JavaBeans from Java 1.1, Sun gave a multi-platform model for software components. The history is repeating itself. Java 3D, which is an extension of Java 1.2 is layering over the mostly spread 3D APIs to bring same 3D graphics everywhere. I'm wondering: What will be in Java 1.3?

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About the author

Andrei Cioroianu (andcio@hotmail.com) is an independent Java developer and holds a BS in Mathematics-Computer Science and an MS in Artificial Intelligence. His focus is on 3D Graphics (Java 3D), Software Components (JavaBeans), and User Interface (AWT, JFC). Before Java 3D API was released, he created applets with 3D graphics using pure Java. Before he became a Java programmer, he developed 3D graphics applications using C/C++/ASM.

RightSpace - CAD application based on Java 3D

The author of this page can be reached at andcio@hotmail.com.
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Last updated: December 30, 1998