/*
 *  alpha3D.java
 *  This program demonstrates how to intermix opaque and
 *  alpha blended polygons in the same scene, by using 
 *  glDepthMask.  Press the 'a' key to animate moving the 
 *  transparent object through the opaque object.  Press 
 *  the 'r' key to reset the scene.
 */

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

public class alpha3D extends GLApplet {

    private static final float MAXZ =  8.0f;
    private static final float MINZ = -8.0f;
    private static final float ZINC =  0.4f;

    private float solidZ = MAXZ;
    private float transparentZ = MINZ;
    private int sphereList, cubeList;

    private void myinit () {
	float mat_specular[] = { 1.0f, 1.0f, 1.0f, 0.15f };
	float mat_shininess[] = { 100.0f };
	float position[] = { 0.5f, 0.5f, 1.0f, 0.0f };

	myGL.glMaterialfv (GL.GL_FRONT, GL.GL_SPECULAR, mat_specular);
	myGL.glMaterialfv (GL.GL_FRONT, GL.GL_SHININESS, mat_shininess);
	myGL.glLightfv (GL.GL_LIGHT0, GL.GL_POSITION, position);

	myGL.glEnable (GL.GL_LIGHTING);
	myGL.glEnable (GL.GL_LIGHT0);
	myGL.glEnable (GL.GL_DEPTH_TEST);

	sphereList = myGL.glGenLists (1);
	myGL.glNewList (sphereList, GL.GL_COMPILE);
	    myUT.glutSolidSphere (0.4f, 16, 16);
	myGL.glEndList ();

	cubeList = myGL.glGenLists (1);
	myGL.glNewList (cubeList, GL.GL_COMPILE);
	    myUT.glutSolidCube (0.6f);
	myGL.glEndList ();
    }

    public void display () {
	float mat_solid[] = { 0.75f, 0.75f, 0.0f, 1.0f };
	float mat_zero[] = { 0.0f, 0.0f, 0.0f, 1.0f };
	float mat_transparent[] = { 0.0f, 0.8f, 0.8f, 0.6f };
	float mat_emission[] = { 0.0f, 0.3f, 0.3f, 0.6f };

	myGL.glClear (GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);

	myGL.glPushMatrix ();
	    myGL.glTranslatef (-0.15f, -0.15f, solidZ);
	    myGL.glMaterialfv (GL.GL_FRONT, GL.GL_EMISSION, mat_zero);
	    myGL.glMaterialfv (GL.GL_FRONT, GL.GL_DIFFUSE, mat_solid);
	    myGL.glCallList (sphereList);
	myGL.glPopMatrix ();

	myGL.glPushMatrix ();
	    myGL.glTranslatef (0.15f, 0.15f, transparentZ);
	    myGL.glRotatef (15.0f, 1.0f, 1.0f, 0.0f);
	    myGL.glRotatef (30.0f, 0.0f, 1.0f, 0.0f);
	    myGL.glMaterialfv (GL.GL_FRONT, GL.GL_EMISSION, mat_emission);
	    myGL.glMaterialfv (GL.GL_FRONT, GL.GL_DIFFUSE, mat_transparent);
	    myGL.glEnable (GL.GL_BLEND);
	    myGL.glDepthMask (GL.GL_FALSE);
	    myGL.glBlendFunc (GL.GL_SRC_ALPHA, GL.GL_ONE);
	    myGL.glCallList (cubeList);
	    myGL.glDepthMask (GL.GL_TRUE);
	    myGL.glDisable (GL.GL_BLEND);
	myGL.glPopMatrix ();

	myGL.glFlush ();
    }

    public void myReshape (int w, int h) {
    	myGL.glViewport (0, 0, w, h);
	myGL.glMatrixMode (GL.GL_PROJECTION);
	myGL.glLoadIdentity ();
        if (w <= h) {
            myGL.glOrtho (-1.5f,   1.5f, 
	    		  -1.5f*(float)h/(float)w, 
			   1.5f*(float)h/(float)w,
			  -10.0f, 10.0f);
        } else {
            myGL.glOrtho ( -1.5f*(float)w/(float)h,
	    		    1.5f*(float)w/(float)h,
			   -1.5f,  1.5f,
			  -10.0f, 10.0f);
        }
	myGL.glMatrixMode (GL.GL_MODELVIEW);
	myGL.glLoadIdentity ();
    }

    public void animate () {
	if (solidZ <= MINZ || transparentZ >= MAXZ)
	    myUT.glutIdleFunc (null);
	else {
	    solidZ -= ZINC;
	    transparentZ += ZINC;
	    myUT.glutPostRedisplay ();
	}
}

    public void keyboard (char key, int x, int y) {
        switch (key) {
            case 'a':
            case 'A':
		solidZ = MAXZ;
		transparentZ = MINZ;
		myUT.glutIdleFunc ("animate");
                break;
            case 'r':
            case 'R':
		solidZ = MAXZ;
		transparentZ = MINZ;
		myUT.glutPostRedisplay ();
                break;
            default:
                break;
        }
    }

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

}