/*
 * Wave.java
 */

import com.sun.opengl.util.FPSAnimator;
import com.sun.opengl.util.GLUT;
import java.awt.BorderLayout;
import javax.media.opengl.GL;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCanvas;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.glu.GLU;
import javax.swing.JFrame;


/**
 * Demonstrates how to plot a 2D surface as a wireframe.
 */
public class Wave implements GLEventListener {
    private GLU glu = new GLU(); // OpenGL Utility Library - used to set camera view
    
    private FPSAnimator anim;    // object used to do the animation
    private double angle = 0.0;  // angle of teapot at each frame
    private int fps = 10;  // frames per second
    
    /**
     * Creates a new instance of Wave
     */
    public Wave() {
    }
    
    /**
     * Initializes parameters.
     * @param d  Object that provides support for OpenGL rendering.
     **/
    public void init( GLAutoDrawable d ) {
        GL gl = d.getGL();
        gl.glClearColor( .2f,.2f,.5f,0 );
        
        gl.glMatrixMode(GL.GL_PROJECTION);
        gl.glLoadIdentity();
        glu.gluPerspective(20.0f, 1.0f, 1.0f, 200.0f);
        gl.glMatrixMode(GL.GL_MODELVIEW);
        
        gl.glEnable(GL.GL_DEPTH_TEST);
        
        anim = new FPSAnimator(d, fps);
        anim.start();
    }
    
    /**
     * Draws what is on the canvas. Here we are drawing a 2D function
     * computed at points on a grid where the value of the function is
     * represented by the z component.  The resulting surface is drawn
     * as a wire frame. The function is a radial cos.
     * @param d  Object that provides support for OpenGL rendering.
     **/
    public void display(GLAutoDrawable d) {
        angle += 1;
        if( angle > 360. ) angle -= 360.0;
        
        GL gl = d.getGL();
        gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
        gl.glMatrixMode(GL.GL_MODELVIEW);
        gl.glLoadIdentity();
        glu.gluLookAt(0,8,4,0,0,0,0,0,1);
        gl.glRotated(angle,0,0,1);
        
        gl.glColor3d(1,1,0);
        
        double range = 4; // side length = 2*range
        int n = 60; // number of grids along edge
        double grid  = 2*range/n; //size of one grid
        for (int i = 0; i < n; i++) {
            for (int j=0; j < n; j++) {
                double x = i*grid - range;
                double y = j*grid - range;
                double xx = x + grid, yy = y + grid;                               
                gl.glBegin(GL.GL_LINE_STRIP);
                    gl.glVertex3d(x, y, f(x,y));
                    gl.glVertex3d(x, yy, f(x, yy));
                    gl.glVertex3d(xx, yy, f(xx, yy));
                    gl.glVertex3d(xx, y, f(xx,y));
                gl.glEnd();
                
                // This will render surface as checkerboard solid, not wireframe.
//                if ((i+j)%2==0) gl.glColor3d(1,0,0);
//                else gl.glColor3d(0,1,0);
//                gl.glBegin(GL.GL_QUADS);
//                    gl.glVertex3d(x, y, f(x,y));
//                    gl.glVertex3d(x, yy, f(x, yy));
//                    gl.glVertex3d(xx, yy, f(xx, yy));
//                    gl.glVertex3d(xx, y, f(xx,y));
//                gl.glEnd();
            }
        }
        
        
        
        
    }
    
    /**
     * Compute the value of function being plotted, f(x,y) = .5*cos(x^2+y^2)
     * @param x x value where function is computed.
     * @param y y value where function is computed.
     */
    public double f(double x, double y) {
        return .5*Math.cos(x*x + y*y);
    }
    
    
    /**
     * Called when the window is resized.
     * @param d  Object that provides support for OpenGL rendering.
     * @param x horizontal location of upper left corner of window.
     * @param y vertical location of upper left corner of window.
     * @param width width of window.
     * @param height height of window.
     **/
    public void reshape(GLAutoDrawable d, int x, int y, int width, int height ){
        GL gl = d.getGL();
        gl.glViewport(0,0, width, height);
        gl.glMatrixMode(GL.GL_PROJECTION);
        gl.glLoadIdentity();
        glu.gluPerspective(60.,(double)width/height, 1.0, 300.);
        gl.glMatrixMode(GL.GL_MODELVIEW);
    }
    
    /**
     * Starting point of execution.
     * @param args  command line arguments. Not used here.
     **/
    public static void main( String[] args ) {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        
        GLCanvas canvas = new GLCanvas();
        canvas.setSize(400,400);
        canvas.addGLEventListener( new Wave() );
        frame.getContentPane().add( canvas, BorderLayout.CENTER );
        
        frame.pack();
        frame.setVisible( true );
    }
    
    /**
     * Called by the drawable when the display mode or the display device associated
     * with the GLAutoDrawable has changed. Not used here but must be included
     * for interface.
     **/
    public void displayChanged( GLAutoDrawable d, boolean modeChanged,
            boolean deviceChanged ) { }
    
}