/*
 *  texgen.java
 *  This program draws a texture mapped teapot with 
 *  automatically generated texture coordinates.  The
 *  texture is rendered as stripes on the teapot.
 *  Initially, the object is drawn with texture coordinates
 *  based upon the object coordinates of the vertex
 *  and distance from the plane x = 0.  Pressing the 'e'
 *  key changes the coordinate generation to eye coordinates
 *  of the vertex.  Pressing the 'o' key switches it back
 *  to the object coordinates.  Pressing the 's' key 
 *  changes the plane to a slanted one (x + y + z = 0).
 *  Pressing the 'x' key switches it back to x = 0.
 */

import java.awt.Frame;
import java.io.IOException;
import java.lang.String;
import java.lang.System;

import jgl.GL;
import jgl.GLCanvas;

public class texgen extends GLCanvas {

    private static final int stripeImageWidth = 32;
    private byte stripeImage[][] = new byte [stripeImageWidth][4];

    private void makeStripeImage () {
	int j;

	for (j = 0; j < stripeImageWidth; j++) {
	    if (j<=4) stripeImage[j][0] = (byte)255;
	    else      stripeImage[j][0] = (byte)0;
	    if (j> 4) stripeImage[j][1] = (byte)255;
	    else      stripeImage[j][1] = (byte)0;
	    stripeImage[j][2] = (byte)0;
	    stripeImage[j][3] = (byte)255;
	}
    }

    /* planes for texture coordinate generation */
    private float xequalzero[] = {1.0f, 0.0f, 0.0f, 0.0f};
    private float slanted[] = {1.0f, 1.0f, 1.0f, 0.0f};
    private float currentCoeff[];
    private int currentPlane;
    private int currentGenMode;

    private void myinit () {
	myGL.glClearColor (0.0f, 0.0f, 0.0f, 0.0f);
	myGL.glEnable (GL.GL_DEPTH_TEST);
	myGL.glShadeModel (GL.GL_SMOOTH);

	makeStripeImage();
	myGL.glPixelStorei(GL.GL_UNPACK_ALIGNMENT, 1);

	myGL.glTexParameterf(GL.GL_TEXTURE_1D, GL.GL_TEXTURE_WRAP_S, GL.GL_REPEAT);
	myGL.glTexParameterf(GL.GL_TEXTURE_1D, GL.GL_TEXTURE_MAG_FILTER, GL.GL_LINEAR);
	myGL.glTexParameterf(GL.GL_TEXTURE_1D, GL.GL_TEXTURE_MIN_FILTER, GL.GL_LINEAR);
	myGL.glTexImage1D(GL.GL_TEXTURE_1D, 0, 4, stripeImageWidth, 0,
                 GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, stripeImage);

	myGL.glTexEnvf(GL.GL_TEXTURE_ENV, GL.GL_TEXTURE_ENV_MODE, GL.GL_MODULATE);
	currentCoeff = xequalzero;
	currentGenMode = GL.GL_OBJECT_LINEAR;
	currentPlane = GL.GL_OBJECT_PLANE;
	myGL.glTexGeni(GL.GL_S, GL.GL_TEXTURE_GEN_MODE, currentGenMode);
	myGL.glTexGenfv(GL.GL_S, currentPlane, currentCoeff);

	myGL.glEnable (GL.GL_TEXTURE_GEN_S);
	myGL.glEnable (GL.GL_TEXTURE_1D);
	myGL.glEnable (GL.GL_CULL_FACE);
	myGL.glEnable (GL.GL_LIGHTING);
	myGL.glEnable (GL.GL_LIGHT0);
	myGL.glEnable (GL.GL_AUTO_NORMAL);
	myGL.glEnable (GL.GL_NORMALIZE);
	myGL.glFrontFace (GL.GL_CW);
	myGL.glCullFace (GL.GL_BACK);
	myGL.glMaterialf (GL.GL_FRONT, GL.GL_SHININESS, 64.0f);
    }

    public void display () {
	myGL.glClear (GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);

	myGL.glPushMatrix ();
	myGL.glRotatef (45.0f, 0.0f, 0.0f, 1.0f);
	myUT.glutSolidTeapot(2.0);
	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 (-3.5f, 3.5f,
			  -3.5f*(float)h/(float)w, 
			   3.5f*(float)h/(float)w, 
			  -3.5f, 3.5f);
        } else {
            myGL.glOrtho (-3.5f*(float)w/(float)h,
			   3.5f*(float)w/(float)h,
			  -3.5f, 3.5f,
			  -3.5f, 3.5f);
        }
        myGL.glMatrixMode (GL.GL_MODELVIEW);
        myGL.glLoadIdentity ();
    }

    /* ARGSUSED1 */
    public void keyboard (char key, int x, int y) {
	switch (key) {
	    case 'e':
	    case 'E':
		currentGenMode = GL.GL_EYE_LINEAR;
		currentPlane = GL.GL_EYE_PLANE;
		myGL.glTexGeni (GL.GL_S, GL.GL_TEXTURE_GEN_MODE, currentGenMode);
		myGL.glTexGenfv (GL.GL_S, currentPlane, currentCoeff);
		myUT.glutPostRedisplay ();
		break;
	    case 'o':
	    case 'O':
		currentGenMode = GL.GL_OBJECT_LINEAR;
		currentPlane = GL.GL_OBJECT_PLANE;
		myGL.glTexGeni (GL.GL_S, GL.GL_TEXTURE_GEN_MODE, currentGenMode);
		myGL.glTexGenfv (GL.GL_S, currentPlane, currentCoeff);
		myUT.glutPostRedisplay ();
		break;
	    case 's':
	    case 'S':
		currentCoeff = slanted;
		myGL.glTexGenfv (GL.GL_S, currentPlane, currentCoeff);
		myUT.glutPostRedisplay ();
		break;
	    case 'x':
	    case 'X':
		currentCoeff = xequalzero;
		myGL.glTexGenfv (GL.GL_S, currentPlane, currentCoeff);
		myUT.glutPostRedisplay ();
		break;
	    case 27:
		System.exit(0);
	    default:
		break;
	}
    }

    public void init () {
	myUT.glutInitWindowSize (200, 200);
	myUT.glutInitWindowPosition (0, 0);
	myUT.glutCreateWindow (this);
	myinit ();
	myUT.glutDisplayFunc ("display");
	myUT.glutReshapeFunc ("myReshape");
	myUT.glutKeyboardFunc ("keyboard");
	myUT.glutMainLoop ();
    }

    static public void main (String args[]) throws IOException {
	Frame mainFrame = new Frame ();
	mainFrame.setSize (208, 227);
	texgen mainCanvas = new texgen ();
	mainCanvas.init();
	mainFrame.add (mainCanvas);
	mainFrame.setVisible (true);
    }

}