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  How to set OpenGL for 2D rendering?  (Read 731 times)
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Offline matthewbot

Innocent Bystander





« Posted 2006-04-12 20:33:13 »

Well, I'm working on a game engine for my future projects. I started out on Java2D, and had pre-rendered sprite operations, dynamic resource management, event system, primitive sound, working, with the foundation for a network layer, when I decided to run some performance tests. I was a bit dissappointed that I could only get 100 mindless rotated and scaled sprites barely above 60 fps, which would leave little time to do other things (eg, actual game/network logic). Enabling the expiremental OpenGL layer, only brought it up to 70, but seemed pretty constant until about 500 instances or so. But seeing as how you cannot webstart the OpenGL layer in Java2D, I decided to overhaul my engine to use JOGL.

After the massive refactoring (I had Graphics2D refrences scribbled everywhere), I've noticed that the first primitive I've coded, the rectangle, doesn't render properly. At one time, it was the wrong size, and the upper right hand corner pixel wasn't drawn. With tinkering, I've gotten that pixel filled, but the rectangle still isn't the right size. The perfectionist in me won't let me cheat and fudge the numbers in my rectangle rendering function. I'm totally new at JOGL, but know Java fairly well. What should I put in my GLEventListener's init() and reshape() methods to get openGL rendering properly for a 2D game?

In case it matters, heres what I've got now:
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   public void init(GLDrawable drawable) {
      GL gl = drawable.getGL();
      gl.glEnable(GL.GL_TEXTURE_2D);
      gl.glClearColor(0, 0, 0, 0);
      gl.glViewport(0, 0, width, height);
      gl.glDisable(GL.GL_DEPTH_TEST);
      new TextureManager(gl); // no need to keep it, has a factory method TextureManager.getTextureManager()
   }
   public void display(GLDrawable drawable) {
      GL gl = drawable.getGL();
     
      gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
      gl.glMatrixMode(GL.GL_MODELVIEW);
      gl.glLoadIdentity();
     
      g.doLoop(new GLGraphicsOutput(gl));
     
      gl.glFlush();
     
   }
   public void reshape(GLDrawable drawable, int x, int y, int width, int height) {
      GL gl = drawable.getGL();
      GLU glu = drawable.getGLU();
     
      gl.glViewport(0, 0, width, height);
      gl.glMatrixMode(GL.GL_PROJECTION);
      gl.glLoadIdentity();
      glu.gluOrtho2D(0, width, height, 0);
   }


Oh! And one more thing. Looking over my code makes me realize that I'm saving my GL from the GLDrawable in init() in a global class TextureManager(), which goes on to use it to load things as needed in display(). Is it ok to do this, or should I use the GL from display()? Does it even matter?
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