Java 3D FAQ - Tim Bray's Running Java3D in a Browser

Tim Bray provided the following information on how to get Java 3D applets working in your browser.

I spent most of the weekend fighting this. Eventually I'll get around to writing a real HOWTO, but maybe this will help some other folks out.

It can be done. I've run it under IE5 and Nav 4.61 on WinNT Workstation and Win95. For now, I'm specializing on IE because the right way to do this is with the <OBJECT> tag and I refuse to use the egregious netscape <APPLET>/<EMBED> botch.
Go get the instructions at Tornado Labs, specifically http://www.tornadolabs.com/News/Java_3D_Installation/java_3d_installation.html and follow them. I have a feeling that maybe half the steps are not actually necessary with recent J3Ds and JDKs, but I don't know which half.
The installs for JDK and J3D and JRE are all by default in different (and I think arguably wrong) places. I haven't figured out what the real right place is - see below.
Installing the JRE installs the Java plug-in so you can run 1.2. After this, your "start" menu will have a "Java Plugin Control Panel". Pop this up and enable the plugin console. You must do this because it is 100% certain that your applet won't run at first, and if you really know java and windows you can actually use the error messages to figure out what's going on. In particular, when it blows up, go hit the jdk1.2.2 javadocs on the actual exception that occurred - sometimes the name of the exception doesn't tell you anything useful but there will be good stuff in the javadoc.
If you're using the
tag to run the plugin, here's an example of some working HTML code:
<OBJECT classid='clsid:8AD9C840-044E-11D1-B3E9-00805F499D93'
width='547' height='453'
java_codebase='http://java.sun.com/products/plugin/1.2/jinstall-12-win32.cab#Version=1,2,0,0'
style='position:absolute;top:50;left:91; height:453;width:547;'>
<PARAM NAME='java_code' VALUE='Browser.class'>
<PARAM NAME='archive' VALUE='Browser.jar'>
<PARAM NAME='codebase' VALUE='/browser/'>
<PARAM NAME='java_type' VALUE='application/x-java-applet;version=1.2'>
<PARAM NAME='ash_path' VALUE='1.7.6.6.7.6.5.9.1.8'>
<PARAM NAME='ash_x' VALUE='4695557'>
<PARAM NAME='ash_z' VALUE='1411584'>
</OBJECT>

Of course a lot of this is specific to my app. Once again, I'm not sure if all of it is really necessary. Observe that you have to give the codebase and any applet parameters (in my case prefixed with "ash_") in elements; the codebase= attribute is ignored.
If you're like most J3D newbies, your mainline will be cut-n-pasted from either the tutorial examples or the ones that come with j3d itself. These all are of the form
```
 public class Foo extends Applet {
   public Foo {
     ... construct the scene graph ...
   }
   ...
   public static void main(String[] args) {
         Frame frame = new MainFrame(new Foo(), 256, 256);
   }
 }
```
This may work as an App, but it will not work as an applet. No init() or start() or stop() or applet machinery. And furthermore the typical constructor apparently does some no-nos because mine regularly blew up with unhelpful messages. Doh. So since you probably want to debug as an app and run as an applet, you'll end up with a fairly complex mainline class that has an init() and start() and some state variables saying whether it's in an applet and a main that calls the init() and start() and so on. In my case I ended up with no constructor at all, using the default applet constructor. It would be real nice if the j3d group would publish a sample one of these that actually works.
I haven't doped out yet what you should do in the stop() & destroy() applet methods; the winNT task manager seems to tell me that java goes to sleep once the browser moves on on from the page with my applet, so for now I'm not doing anything there.
Path and classpath will cause you problems. There is no documentation that says where the java plugin actually goes to look for classes; I seemed to need to set the classpath on win95 but not winNT. If you end up having the .class files in c:\jdk1.2.2\...\lib and ...\lib\ext and \Program Files\Javasoft\JRE\1.2\... \lib and ...\ext and maybe a couple other places, eventually the plug-in will find it.
Similarly, the plug-in doesn't say where it actually goes looking for the DLLs it runs that actually implement the J3D stuff. Once again on NT, the installation left it in a place where the plug-in found it, on win95 I ended up copying the DLLs to several \bin directories in parallel with the \lib directories listed above and eventually it found them.

When your applet fails to run, go back to Tornado Labs and see if you can run their Bench3d applet (pointed to from the page mentioned above) - if it doesn't work, the error messages in the java plugin console will probably help you figure out why not.

Immense thanks are due to Mitch Williams and Dan Selman, who helped me bash through some of these steps.

It would be good if the java3d team were to take ownership of this problem and get it in the FAQ, and maybe even arrange that for future releases, if you just install various combinations of jdk/jre/j3d and take all the defaults, you get something that works.
Cheers, Tim
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