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gregorypierce
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How to: Getting started with JOGL
« on: Jul 12th, 2003, 12:39pm » |
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Getting up and running with JOGL JOGL is Sun's open sourced
OpenGL binding for Java. It is actively supported by many developers
with Sun's newly established Java Gaming Group. With JOGL it is
possible to finally be able to create (API supported) OpenGL games in
Java. The only credible competing API is the LWJGL (Lightweight Java
Game Library) which strives to be the Java gaming equivalent of
DirectX.
Both libraries utilize a hefty amount of native code, but where
LWJGL seeks to be a complete gaming solution - the Sun APIs (JOGL,
JOAL, and JInput) allow you to mix and match what you need to create
your solution. In addition, JOGL integrates cleanly with AWT and Swing
components whereas LWJGL creates its own native window - defying any
attempts to integrate it with a Java application.
This article deals specifically with getting JOGL installed on
your machine and getting it to render a single cheesy triangle. As you
will shortly discover, this takes little effort (unless you are
unfamiliar with the OpenGL APIs). The first step required is to obtain
the binaries that you will need in order to compile and run your
applications. These pre-compiled binaries can be obtained from the
project website file sharing area Project Files. Download the binaries
for your platform (currently there are binaries available for OSX
(Panther DP or greater), Linux, Solaris, and Windows. This pretty much
covers all of the major platforms so I doubt you'll find yourself
trying to compile the library yourself.
Now that you have the binaries you will note that you hava a .jar
file and a JNI library (.dll, .so, .jnilib). You will need to install
the jogl.jar file in the classpath of your build environment in order
to be able to compile an application with JOGL. Since many people these
days are using IDEs like Eclipse, JBuilder, and IntelliJ - it is fairly
straightforward to add the .jar file to your build. Follow the
instructions for your specific build environment.
Next comes the slightly trickier part, the installation of the
native library. You won't need this in order to compile your
application, but you will need it in order to run your application.
Java developers usually don't find themselves installing native
libraries (for obvious reasons) so it usually escapes us as to how its
done. Java loads native libraries from the directories listed in the
java.library.path environment variable. Best to just print this out and
put the native library into one of these directories. One of these
directories is likely to be the extension (ext) directory of the JRE
for your IDE. Unless you only want to run the application from inside
the IDE, don't install it here.
You can confirm this by creating a test program that does
System.loadLibrary("jogl");. If the application throws an
UnsatisfiedLinkException, the JRE running your application cannot find
the native library. This isn't too likely if you've installed it in one
of the directories listed in java.library.path, but just in case - try
again 
Now that you have JOGL installed, you want to feed cool L33t
geometry to your video card and have it do cool stuff. Well at the
moment I want to feed myself so I tell you about that. Coming up next -
actually understanding the API enough to be able to get something on
the screen!
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gregorypierce
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Re: How to: Getting started with JOGL
« Reply #1 on: Jul 12th, 2003, 1:15pm » |
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Okay, no food that doesn't require cooking so I will press forward and
cover as much as I can until I pass out from starvation 
You will build your JOGL application much the same as you build any other AWT application (for now):
Code:
Frame testFrame = new Frame("TestFrame");
testFrame.setSize( 512, 384 );
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Note here that I am creating a frame and giving that frame a size.
Since at the moment I don't plan to have any extra stuff in that frame
other than the rendered component this is fine and I won't worry about
a layoutmanager.
The next thing you need is a warm
piece of GLCanvas to draw on. Since you cannot directly instantiate
GLCanvas (which is good OO design) you must obtain it from the factory
that creates them. This is GLDrawableFactory. We will tell this factory
that we want it to create and return to us a GLCanvas with a default
set of capabilities.
Code:
GLCanvas canvas =
GLDrawableFactory.getFactory().createGLCanvas( new GLCapabilities() );
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The capabilities that you want a GLCanvas to have are specified in
GLCapabilities. So if you want something with specific buffers,
bitdepths, etc, you would create a GLCapabilities() object that has
those capabilities and pass that into the factory as so:
Code:
GLCapabilities glCaps = new GLCapabilities();
glCaps.setRedBits(8);
glCaps.setBlueBits(8);
glCaps.setGreenBits(8);
glCaps.setAlphaBits(8);
GLCanvas canvas = GLDrawableFactory.getFactory().createGLCanvas( glCaps );
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There is a lot of stuff you can do with GLCapabilities but I'm not going to cover that here - explore and experiment.
Now that you have your GLCanvas done you need to add it to the Frame so that people will be able to see it.
Code:
So now you have a GLCanvas on a Frame and when that frame comes up it will do.... nothing 
The reason it won't do anything is because of the architecture of JOGL.
JOGL will emit a series of events that will tell you what's going on
with the framework so that you can listen for those events and do the
right thing. JOGL refers to this as a GLEventListener. The
GLEventListener contains the methods that we're most interested in:
init(), display(), reshape(), and displayChanged().
When the GLCanvas (which is a GLDrawable) is rendered for the first
time, init(GLDrawable) is called. In this method you would do the same
thing you would do in an init call to your old OpenGL engines. Set up
any initial settings and get yourself ready to draw. If you aren't
following the JOGL architecture properly, you may be able to hack some
drawing into this method but DO NOT do this. You will make your life
harder later. Load textures, geometry, etc here, but don't start trying
to render anything in this method.
Code:
public void init(GLDrawable drawable)
{
this.gl = drawable.getGL();
this.glDrawable = drawable;
drawable.setGL( new DebugGL(drawable.getGL() ));
System.out.println("Init GL is " + gl.getClass().getName());
}
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When a GLDrawable is told to render, this method is called. Note that
this is a good way to decouple the rendering interface from any sort of
frame rate limiter or timing system. Anyways, THIS is the method where
you want to do your drawing.
Code:
public void display(GLDrawable drawable)
{
gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT );
gl.glLoadIdentity();
gl.glColor3f(1.0f, 0.0f, 0.0f );
gl.glBegin( GL.GL_TRIANGLES );
gl.glVertex3f( 0.0f, 0.0f, 0.0f );
gl.glVertex3f( 1.0f, 0.0f, 0.0f );
gl.glVertex3f( 1.0f, 1.0f, 0.0f );
gl.glEnd();
}
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There has been some question as to whether or not one should reacquire
gl in the display method. I have as of yet found it unnecessary to do
this and I'm not sure why its recommended as the GLDrawable should not
be destroyed at any point during rendering and as such should be
cacheable as should GL and GLU.
The next method
of interest is reshape(). Just like with GLUT, reshape is called when
your context changes shape. Its useful to make camera adjustments and
the like when this occurs in this method. Since I currently don't
support these operations this method is undefined:
Code:
public void reshape(GLDrawable drawable, int x, int y, int width, int height)
{
}
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The same can be said of display changed. If the device or display mode
changes, JOGL will let you know so you can handle your rendering
accordingly.
Code:
public void displayChanged(GLDrawable drawable, boolean modeChanged, boolean deviceChanged)
{
}
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So now you have the code for what I refer to at the TestRenderer, but
you can call it whatever you want so long as it implements
GLEventListener.
Now that you have a GLEventListener lo and behold you application renders... nothing still
The reason is again in the JOGL architecture. Recall that the display
method needs to be called before anything gets drawn to the screen.
Well - you don't have anything calling display(). You COULD throw in a
while loop that spun forever calling display(), but there is really a
better way. JOGL includes the concept of an Animator. This animator
basically holds the tempo of when display gets called. Personally I
think RenderLoop might have been a better name, but hey you can extend
it and call it whatever you want right
To make a long story short you need to add an Animator so that display
is getting called. For this tutorial I will use the one provided for by
JOGL, though one that handles frame rates properly is likely going to
make a LOT more sense for anything running in a Window. No sense having
JOGL running in a window yet taking up so much CPU that nothing else
can really run either. The last chunk of code that you need is
Code:
final Animator animator = new Animator(canvas);
testFrame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
animator.stop();
System.exit(0);
}
});
testFrame.show();
animator.start();
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There you have it. Go ahead and compile/run and you will have one
cheesy triangle. The world is now yours to control because if you can
draw one triangle, you can draw millions of triangles in 3D space with
textures and stuff and have a real game. At this point you might want
to take a look at some OpenGL resources as it won't matter whether or
not you're coding in C++ or Java as OpenGL is OpenGL and it will be
simple to tell what needs to be syntactically changed to work with JOGL
(or LWJGL for that matter).
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| « Last Edit: Jul 12th, 2003, 1:30pm by gregorypierce » |
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gregorypierce
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Re: How to: Getting started with JOGL
« Reply #2 on: Jul 12th, 2003, 1:27pm » |
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Test.java
Code:
import net.java.games.jogl.*;
import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
public class Test
{
public static void main( String[] args )
{
try
{
Frame testFrame = new Frame("TestFrame");
testFrame.setSize( 512, 384 );
GLCapabilities glCaps = new GLCapabilities();
glCaps.setRedBits(8);
glCaps.setBlueBits(8);
glCaps.setGreenBits(8);
glCaps.setAlphaBits(8);
GLCanvas canvas = GLDrawableFactory.getFactory().createGLCanvas( glCaps );
testFrame.add( canvas );
canvas.addGLEventListener(new TestRenderer());
final Animator animator = new Animator( canvas);
testFrame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
animator.stop();
System.exit(0);
}
});
testFrame.show();
animator.start();
}
catch( Exception e )
{
e.printStackTrace();
}
}
}
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TestRenderer.java
Code:
import net.java.games.jogl.GLEventListener;
import net.java.games.jogl.GL;
import net.java.games.jogl.GLDrawable;
import net.java.games.jogl.DebugGL;
public class TestRenderer implements GLEventListener
{
private GL gl;
private GLDrawable glDrawable;
public void init(GLDrawable drawable)
{
this.gl = drawable.getGL();
this.glDrawable = drawable;
drawable.setGL( new DebugGL(drawable.getGL() ));
System.out.println("Init GL is " + gl.getClass().getName());
}
public void display(GLDrawable drawable)
{
gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT );
gl.glLoadIdentity();
gl.glColor3f(1.0f, 0.0f, 0.0f );
gl.glBegin( GL.GL_TRIANGLES );
gl.glVertex3f( 0.0f, 0.0f, 0.0f );
gl.glVertex3f( 1.0f, 0.0f, 0.0f );
gl.glVertex3f( 1.0f, 1.0f, 0.0f );
gl.glEnd();
}
public void reshape(GLDrawable drawable, int x, int y, int width, int height)
{
}
public void displayChanged(GLDrawable drawable, boolean modeChanged, boolean deviceChanged)
{
}
}
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| « Last Edit: Jul 12th, 2003, 1:27pm by gregorypierce » |
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She builds, she builds oh man
When she links, she links I go crazy
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I think I'll run upstairs and grab a snack!
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DavidYazel
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Java games rock!
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Re: How to: Getting started with JOGL
« Reply #3 on: Jul 12th, 2003, 4:47pm » |
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Thank you, that was a nice introduction!
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David Yazel
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http://xith3d.dev.java.net
It may look complicated, but in the end it is just a bunch of triangles
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swpalmer
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Re: How to: Getting started with JOGL
« Reply #4 on: Jul 12th, 2003, 10:28pm » |
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Yes, thanks! That was excellent. Perhaps it should be
placed in the Wiki so that when this thread is long lost this info is
still easy to find.
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Digital Cinema Quacks Sanity
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Archimedes
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Re: How to: Getting started with JOGL
« Reply #5 on: Jul 13th, 2003, 2:43am » |
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A very nice introduction. Simple and robust; so it should be with Java all day. :-)
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Ken Russell
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Re: How to: Getting started with JOGL
« Reply #6 on: Jul 14th, 2003, 7:26am » |
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Thanks for writing this introduction. Do you have it in HTML form?
Let's check it in under the doc/ subdirectory of the jogl project.
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gregorypierce
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Re: How to: Getting started with JOGL
« Reply #7 on: Jul 14th, 2003, 1:07pm » |
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Not yet, but I'll convert it into an HTML form and email it to you. I'm
going to continue on by adding some stuff on getting a textured
triangle since there is some VERY understandable weirdness and
confusion about loading textures and doing some basic input (not using
JInput until I get finished with learning Cocoa to handle input for
OSX).
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She builds, she builds oh man
When she links, she links I go crazy
Cause she looks like good code but she's really a hack
I think I'll run upstairs and grab a snack!
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Markus_Persson
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Re: How to: Getting started with JOGL
« Reply #8 on: Jul 23rd, 2003, 3:25pm » |
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Has anyone gotten this to run on linux?
I was trying to figure out why Wurm was having trouble on linux, so got
rid of everything but the example here and uploaded it.
The Guy(tm) who's running linux (I'm not) gets this:
net.java.games.jogl.GLException: Error making context current
at net.java.games.jogl.impl.x11.X11GLContext.makeCurrent(X11GLContext.java: 141)
at net.java.games.jogl.impl.x11.X11OnscreenGLContext.makeCurrent(X11Onscree nGLContext.java:111)
at net.java.games.jogl.impl.GLContext.invokeGL(GLContext.java:162)
at net.java.games.jogl.GLCanvas.displayImpl(GLCanvas.java:196)
at net.java.games.jogl.GLCanvas.display(GLCanvas.java:91)
at net.java.games.jogl.Animator$1.run(Animator.java:104)
at java.lang.Thread.run(Thread.java:536)
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Current project: Wurm Online
Warning: Current project can and will change at random. In fact, there's even a Random subclass based on that fact.
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gregorypierce
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Re: How to: Getting started with JOGL
« Reply #9 on: Jul 23rd, 2003, 5:06pm » |
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I'll fire up RedHat 9 tonight and see what i can find in terms of
running general applications. I haven't had any problems with Linux in
the past so it would be surprising to find something now.
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She builds, she builds oh man
When she links, she links I go crazy
Cause she looks like good code but she's really a hack
I think I'll run upstairs and grab a snack!
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nlmueng
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Re: How to: Getting started with JOGL
« Reply #10 on: Jul 23rd, 2003, 6:37pm » |
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You need to change the GLCapabilities part. If you just switch it
to say new GLCapabilities() instead of creating a defined one it works
fine. I think it has something to do with being 32 bit.
Nathan
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AndersDahlberg
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Re: How to: Getting started with JOGL
« Reply #11 on: Jul 23rd, 2003, 6:49pm » |
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I'm "the guy(tm)"
Strange thing is, the jogl demos works fine (i.e. gears)!
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gregorypierce
YaBB God
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Re: How to: Getting started with JOGL
« Reply #13 on: Jul 23rd, 2003, 9:03pm » |
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I am able to on RedHat 9 using the latest NVidia drivers on a GeForce
4200 able to get that GLCapabilities() to work. Not sure why yours
wouldn't. You should have enough video memory for that to work unless
you're requesting an incredibly large GLContext, or potentially
something that's non-square'd, though that's rarely an issue these
days.
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http://www.gregorypierce.com
She builds, she builds oh man
When she links, she links I go crazy
Cause she looks like good code but she's really a hack
I think I'll run upstairs and grab a snack!
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nlmueng
YaBB Newbie
Posts: 47
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Re: How to: Getting started with JOGL
« Reply #14 on: Jul 23rd, 2003, 9:37pm » |
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it fails on my box too if I leave it that way. When I just did it like new GLCapabilities() it works.
I only have the 810 onboard video in the box.
nathan
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