/*
 *  movelight.java
 *  This program demonstrates when to issue lighting and
 *  transformation commands to render a model with a light
 *  which is moved by a modeling transformation (rotate or
 *  translate).  The light position is reset after the modeling
 *  transformation is called.  The eye position does not change.
 *
 *  A sphere is drawn using a grey material characteristic.
 *  A single light source illuminates the object.
 *
 *  Interaction:  pressing the left mouse button alters
 *  the modeling transformation (x rotation) by 30 degrees.
 *  The scene is then redrawn with the light in a new position.
 */

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

public class movelight extends GLApplet {

    private int spin = 0;

    /*
     *  Initialize material property, light source, lighting model,
     *  and depth buffer.
     */
    private void myinit () {
    	myGL.glClearColor (0.0f, 0.0f, 0.0f, 0.0f);
	myGL.glShadeModel (GL.GL_SMOOTH);
	myGL.glEnable (GL.GL_LIGHTING);
	myGL.glEnable (GL.GL_LIGHT0);
	myGL.glEnable (GL.GL_DEPTH_TEST);
    }

    /*
     *  Here is where the light position is reset after the modeling
     *  transformation (glRotated) is called.  This places the
     *  light at a new position in world coordinates.  The cube
     *  represents the position of the light.
     */
    public void display () {
    	float position [] = {0.0f, 0.0f, 1.5f, 1.0f};

	myGL.glClear (GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
	myGL.glPushMatrix ();
	    myGLU.gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

	    myGL.glPushMatrix ();
	    	myGL.glRotated ((double)spin, 1.0, 0.0, 0.0);
		myGL.glLightfv (GL.GL_LIGHT0, GL.GL_POSITION, position);

		myGL.glTranslated (0.0, 0.0, 1.5);
		myGL.glDisable (GL.GL_LIGHTING);
		myGL.glColor3f (0.0f, 1.0f, 1.0f);
		myUT.glutWireCube (0.1);
		myGL.glEnable (GL.GL_LIGHTING);
	    myGL.glPopMatrix ();

	    myUT.glutSolidTorus (0.275, 0.85, 8, 15);
	myGL.glPopMatrix ();
	myGL.glFlush ();
    }

    public void myReshape (int w, int h) {
        myGL.glViewport (0, 0, w, h);
        myGL.glMatrixMode (GL.GL_PROJECTION);
        myGL.glLoadIdentity ();
	myGLU.gluPerspective (40.0, (float)w/(float)h, 1.0, 20.0);
        myGL.glMatrixMode (GL.GL_MODELVIEW);
        myGL.glLoadIdentity ();
    }

    /* ARGSUSED2 */
    public void mouse (int button, int state, int x, int y) {
	switch (button) {
	    case GLUT.GLUT_LEFT_BUTTON:
		if (state == GLUT.GLUT_DOWN) {
		    spin = (spin + 30) % 360;
		    myUT.glutPostRedisplay ();
		}
		break;
	    default:
		break;
	}
    }

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

}