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Java wraps native code in Prax War
Written by Billy Zelsnack during his days at Rebel Boat Rocker, Prax War was destined to be the first major game to use Java for most of its code. With the exception of a C renderer, the Prax War engine was written entirely in Java. Zelsnack explained the game this way: "We use JDK and JNI. The game itself starts from Java. I use Java as controller code for C. Java is very good at calling C code, but [it is] not necessarily as clean the other way around." The design kept raw data (such as textures and sounds) on the native side, but made them accessible to Java as needed. Billy Zelsnack found few problems with the core classes (at one point, UDP networking performance was an issue), and found no problems with the most feared Java component, the garbage collector. The engine used just two threads — one thread that listened for incoming packets, plus the main loop itself. Unfortunately, Rebel Boat Rocker's publisher, Electronic Arts, decided earlier this year to cancel the project, stating that the game had "missed its technology window". If Electronic Arts had had the kind of faith in Rebel Boat Rocker that Sierra has shown in Valve Software, we might have found that their assessment was straight to the point — maybe Prax War missed its technology window by being too early.
Zelsnack summed up his Java experience up this way: "Java opened up possibilities for the product that could not have been realized without its power. It was one of the things I was most excited about and proud of." id Abandons Java for Quake 3: Arena John Carmack considered using Java in id's games for quite some time, ever since he announced that the company was leaning towards client-downloadable code for the Trinity project. "The QA game architecture so far has two separate binary .DLLs: one for the server-side game logic, and one for the client side presentation logic." Games that licensed the Quake 2 engine, notably Half-Life and Heretic 2, also wound up using client side .DLLs. However, with the hacking attacks on Quake 2 servers in mind, Carmack states that, "While it was easiest to begin development like that, there are two crucial problems with shipping the game that way: security and portability. If we were willing to wed ourselves completely to the Windows platform, we might have pushed ahead, but I want Quake 3: Arena running on every platform that has hardware-accelerated OpenGL and an Internet connection."
His solution: "I had been working under the assumption that Java was the right way to go, but recently I reached a better conclusion. The programming language is interpreted ANSI C. The game will have an interpreter for a virtual RISC-like CPU." Unreal followed a similar approach: companies that license the engine can opt to use compiled C or C++ code, and interpreted UnrealScript is available for homebrew scripting. The advantages of using a C or C++ subset for your VM are obvious when it comes to handling legacy code. Ironically, it was Java portability problems that led id to develop the Quake 3 custom VM. Sun's promise of "write once, run anywhere" did not hold for the Invocation API on important server platforms, so Carmack decided to abandon the embedded JVM he had planned to use. "My ideal situation," he stated, "would be to include the interpreter in the QUAKE3.EXE, and just treat class files as data to be loaded and dealt with like anything else." Unfortunately, while this solution works fine on Win32 platforms, this was not guaranteed for Linux, OS/2, or even Solaris. "Having made the decision to do my own interpreter, I feel much more at ease not having to rely on anyone else's external code. When it comes around to the next development cycle, I will make the Java decision again." As for embedding: "We are still working with significant chunks of an existing code base. If I did want to go off and start fresh, I would likely try doing almost everything in Java." Embedded Java in Vampire: The Masquerade In a recent developer update, Nihilistic's Director of Technology, Robert Huebner, stated: "I've always been rather anti-Java; all the Internet hype surrounding the language was overwhelming. But after examining the language further, it was clear that it makes an ideal scripting language for games. The embedded Java API allows us to provide our designers with a subset of the Java environment, and the JNI interface allows us to provide hooks from the Java Virtual Machine (JVM) directly into the game engine." The new Java-based system for their next game, Vampire: The Masquerade, will replace a custom compiled language, COG, that the team used in its previous title, Jedi Knight: Dark Forces 2. According to Huebner, "The JVM is a lot faster than the systems we wrote ourselves; their kernel is more heavily optimized, the available Java compilers produce much more optimized object code, and the newest JVM systems include just-in-time (JIT) compilation to native instructions as a standard feature. And since the language is so much richer than our previous C-subset, it gives the designers a much wider range of possibilities." Because Nihilistic is developing primarily for Windows, it is able to apply solutions that were not feasible for id Software's multi-platform Quake 3: Arena strategy.
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