Using JVerge

The Package Structure

• vlc.vrml.external.geometry For use with applets
• vlc.vrml.internal.geometry For use with VRML scripts
• vlc.vrml.generic.geometry For use with standalone applications

Class Overview

There are then three main methods that are used:

The first is cleanup. Cleanup looks after the internal cleaning up, any reference counting and stuff like that. It should be called just before you remove any reference to this node when you are creating a subclass of VrmlObject. In normal day to day use of the classes there is no need for you to use this method at all. If your derived class contains MF/SFNodes then it should recursively call the cleanup methods of those nodes as well.

The second method is called writeReset. This is should be called immediately before starting to write this node to a file. Like cleanup, it is recursive and looks after any children nodes that might exist.

The final method is the abstract method writeToStream which takes two arguments. The first is a PrintStream and the second is the level of indent. For most applications this should start at zero and then let JVerge take care of the indenting internally.

For all the classes there is a default constructor supplied. This will create an instance of the node that is completely default as per the VRML 97 spec. For nodes where you want to supply non-defualt values for any field type fields then another constructor is provided for that. In the case where you have a number of different browsers there is also variants on the above two methods that include a Browser reference as the first argument. The other constructors use the static reference that is contained within the class.

Writing Code

Simplest approach

import vlc.vrml.external.geometry.*;

public class myApplet extends applet
{
        Browser browser;

	public void start()
	{
		Browser = Browser.getBrowser(this);
		// etc
	}

	{
	        // in a method somewhere deep in the code....
		Transform tx = new Transform(Browser);

	        // then you need to add this to some
		// pre-existing node in the scene.
		some_SFNode_eventIn.setValue(tx.node);
	}
}

An Alternative Constructor

import vlc.vrml.external.geometry.*;

public class myApplet extends applet
{
        Browser browser;

	public void start()
	{
		browser = Browser.getBrowser(this);

		VrmlObject.set_browser(browser);
		// etc
	}

        // in a method somewhere deep in the code....
	{
		Transform tx = new Transform();

	        // then you need to add this to some
		// pre-existing node in the scene.
		some_SFNode_eventIn.setValue(tx.node);
	}
}

I recommend this approach is the better to use if you are going to be creating a lot of nodes. I would only use the former when I was running an applet that was talking to two or more browsers at the same time where the two Browser references will be different, depending on which one you are creating geometry for.

Combining nodes together

import vlc.vrml.external.geometry.*;

public class myApplet extends applet
{
        Browser browser;

	public void start()
	{
		browser = Browser.getBrowser(this);

		VrmlObject.set_browser(browser);
		// etc
	}

        // in a method somewhere deep in the code....
	{
		float[] color = {1, 0, 0};

	        Shape shape = new Shape();
        	Box box = new Box(2, 3, 4);
	        Appearance app = new Appearance();
        	Material mat = new Material();

	        // set the material to red
        	mat.set_diffuseColor(color)

	        // now combine them all together
        	shape.set_geometry(box);
	        shape.set_appearance(app);
        	app.set_material(mat);

        // then you need to add this to some pre-existing node in the scene.
}

Printing Out the Scenegraph

JVerge is deliberately very lax about where it writes the data to. So long as a PrintStream is provided then that is all that is needed. Just open a stream connected to a socket or a file and off you go. The following code is taken from VermelGen that writes the output to a String.

import java.io.*;
import vlc.vrml.external.geometry.*;

public class VrmlScene
{
	private Browser		browser;
	private VrmlRoot	file_root;

	// lots of snipped code!

	public String getSceneDescription()
	{
		ByteArrayOutputStream os = new ByteArrayOutputStream();
		PrintStream ps = new PrintStream(os);

		file_root.writeToStream(ps);

		String output = os.toString();

		try
		{
			ps.close();
			os.close();
		}
		catch(IOException e)
		{
			System.out.println("Error closing output streams");
		}

		return(output);
	}
}

import java.io.*;
import java.util.*;
import vlc.vrml.external.geometry.*;

public class VrmlRoot extends GroupingNode
{
	// lots of code snipped from here

	public void writeToStream(PrintStream fp)
	{
		Enumeration e = _children.elements();

		// firstly we need to reset the contents of the file
		for(; e.hasMoreElements();)
			((VrmlObject)(e.nextElement())).writeReset();

		fp.println("#VRML V2.0 utf8");
		fp.println("#");
		fp.println("# Generated by the VermelGen http://www.vlc.com.au/VermelGen/");
		fp.println("# GNU Software by The Virtual Light Company");
		fp.println("# Released under the GPL ftp://ftp.sunsite.edu/pub/GNU/copyinfo.txt");
		fp.println("");

		e = _children.elements();

		for(; e.hasMoreElements();)
			((VrmlObject)(e.nextElement())).writeToStream(fp, 0);
	}
}