/*
 *  unproject.java
 *  When the left mouse button is pressed, this program 
 *  reads the mouse position and determines two 3D points 
 *  from which it was transformed.  Very little is displayed.
 */
import java.lang.System;

import jgl.GL;
import jgl.GLU;
import jgl.GLUT;
import jgl.GLApplet;

public class unproject extends GLApplet {

    public  void display () {
	myGL.glClear (GL.GL_COLOR_BUFFER_BIT);
	myGL.glFlush ();
    }

    /*
     * Change these values for a different transformation
     */
    public void myReshape (int w, int h) {
	myGL.glViewport (0, 0, w, h);
	myGL.glMatrixMode (GL.GL_PROJECTION);
	myGL.glLoadIdentity ();
	myGLU.gluPerspective (45.0, (float)w/(float)h, 1.0, 100.0);
	myGL.glMatrixMode (GL.GL_MODELVIEW);
	myGL.glLoadIdentity ();
    }

    public void mouse (int button, int state, int x, int y) {
	int viewport[] = new int [4];
	double mvmatrix[] = new double [16], projmatrix[] = new double [16];
	int realy;			/*  OpenGL y coordinate position  */
	double wx[] = new double [1],
	       wy[] = new double [1],
	       wz[] = new double [1];	/*  returned world x, y, z coords  */

	switch (button) {
	    case GLUT.GLUT_LEFT_BUTTON:
		if (state == GLUT.GLUT_DOWN) {
		    myGL.glGetIntegerv (GL.GL_VIEWPORT, viewport);
		    myGL.glGetDoublev (GL.GL_MODELVIEW_MATRIX, mvmatrix);
		    myGL.glGetDoublev (GL.GL_PROJECTION_MATRIX, projmatrix);
		    /*  note viewport[3] is height of window in pixels  */
		    realy = viewport[3] - y - 1;
		    System.out.println ("Coordinates at cursor are ("+x+", "+realy+")");
		    myGLU.gluUnProject (x, realy, 0.0, mvmatrix, projmatrix, viewport, wx, wy, wz); 
		    System.out.println ("World coords at z=0.0 are ("+wx[0]+", "+wy[0]+", "+wz[0]+")");
		    myGLU.gluUnProject (x, realy, 1.0, mvmatrix, projmatrix, viewport, wx, wy, wz); 
		    System.out.println ("World coords at z=1.0 are ("+wx[0]+", "+wy[0]+", "+wz[0]+")");
		}
		break;
	    default:
		break;
	}
    }

    public void init () {
	myUT.glutInitWindowSize (500, 500);
	myUT.glutInitWindowPosition (0, 0);
	myUT.glutCreateWindow (this);
	myUT.glutDisplayFunc ("display");
	myUT.glutReshapeFunc ("myReshape"); 
	myUT.glutMouseFunc ("mouse");
	myUT.glutMainLoop ();
    }

}