JOGL - open GL - keeping part of the world stationary while moving the rest

I'm kind of new to JOGL, and I am working on a game. I have a rocket, stars in the background, and planets. I want the rocket to remain stationary at the bottom of the screen, the GO button to be pressed, and then planets start coming down for the rocket to avoid.

I keep ending up w开发者_C百科ith hitting go, the planets coming down (via translation), and the rocket also going down. I know Why this is happened with the camera moving, so the whole world is moving. I've been trying to use the pushMatrix and popMatrix, but haven't had any luck.

i.e.

if (goButtonPressed)  
{
    //gl.glTranslatef(0.0f,0.3f,0f);   // this line just keeps the whole thing still  
    drawRocket(gl);                    // I was trying to 'undo' the translation  
    gl.glPushMatrix();  
    gl.glMatrixMode(GL.GL_PROJECTION);  
    gl.glTranslatef(0.0f, -0.3f, 0f);  
    gl.glPopMatrix();  
}

Is what I am trying to do possible in opengl? Am I making it too difficult?

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Instead of relying on the projection matrix to hold the state of your rockets' positions, how about storing this information in your own code and then passing absolute coordinates to JOGL? Then updating the position of an object can be done with a more obvious bit of code like rocket.y += dy;.

As a small aside, the projection matrix is not intended to be used for spatial transformations. Use GL_MODELVIEW instead to avoid subtle problems down the road.

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Not exactly an answer to your question, but you should look at JMonkeyEngine if you want to make a game with opengl in Java.

http://jmonkeyengine.com/

The thing you are trying to do is certainly possible with opengl and fairly easy to do with JMonkeyEngine. They have plenty of tutorials and such on their site.