DIY 3D Library

Test.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.io.*;
import java.util.*;
import static java.lang.Math.*;

public class Test extends JPanel {

    private ArrayList<Vertex> vertices = null;
    private ArrayList<Face> faces = null;
    private Point center = null;
    private Point mousePos = null;
    private double scale;
    private double phi;    // x axis
    private double theta;  // y axis 
    private int WIDTH;
    private int HEIGHT;

    public Test(int width, int height) {
	super(true);

	this.WIDTH = width;
	this.HEIGHT = height;
	this.center = new Point(WIDTH/2, HEIGHT/2);
	this.scale = WIDTH * 0.8 / 2;
	setSize(width, height);
	setPreferredSize(new Dimension(WIDTH,HEIGHT));

	this.vertices = new ArrayList<Vertex>();
	this.faces = new ArrayList<Face>();

	this.mousePos = new Point(0,0);

	// Angles of rotation
	this.phi = 0.0;
	this.theta = 0.0;

       	MouseInputListener adapter = new MouseInputAdapter() {
		public void mouseDragged(MouseEvent e){
		    theta += (e.getX() - mousePos.x) * 0.01;
		    phi   += (e.getY() - mousePos.y) * 0.01;

		    phi = min(phi, PI/2);
		    phi = max(phi, -PI/2);

		    mousePos.setLocation(e.getX(), e.getY());

		    refreshScreenPosition();

		    repaint();
		}

		public void mousePressed(MouseEvent e){
		    mousePos.setLocation(e.getX(), e.getY());
		}
	    };

	addMouseMotionListener(adapter);
	addMouseListener(adapter);

	setModelData();
    }

    public void paintComponent(Graphics g) {
	drawModel(g);
    }

    private void refreshScreenPosition() {
	for(Vertex v:vertices){
	    v.rx = v.x * cos(theta) + v.z * sin(theta);
	    v.ry = v.x * sin(phi) * sin(theta) + v.y * cos(phi) - v.z * sin(phi) * cos(theta);
	    v.rz = -v.x * cos(phi) * sin(theta) + v.y * sin(phi) + v.z * cos(phi) * cos(theta);
	}

	for(Face face:faces){
	    // refresh a depth
	    face.z = 0.0;
	    for(int i=0;i<3;i++) face.z += face.v[i].rz;
	    face.z /= 3.0;

	    double ax = face.v[1].rx - face.v[0].rx;
	    double ay = face.v[1].ry - face.v[0].ry;
	    double az = face.v[1].rz - face.v[0].rz;
	    double bx = face.v[2].rx - face.v[0].rx;
	    double by = face.v[2].ry - face.v[0].ry;
	    double bz = face.v[2].rz - face.v[0].rz;

	    face.nx = ay * bz - az * by;
	    face.ny = az * bx - ax * bz;
	    face.nz = ax * by - ay * bx;

	    double l = sqrt(face.nx * face.nx + face.ny * face.ny + face.nz * face.nz);
	    face.nx /= l;
	    face.ny /= l;
	    face.nz /= l;
	}

	Collections.sort(faces, new Comparator<Face>() {
		public int compare(Face f1, Face f2) {
		    return (f1.z > f2.z)? 1:-1;
		}
	    });
    }

    public void setModelData() {
	double modelSize = 0.0;

	try{
	    Scanner scn = new Scanner(new FileInputStream("file.obj"));
	    while(scn.hasNext("[vf]")){
		String cmd = scn.next("[vf]");
		if(cmd.equals("v")){
		    double x = scn.nextDouble();
		    double y = scn.nextDouble();
		    double z = scn.nextDouble();

		    modelSize = max(modelSize, x, y, z);

		    vertices.add(new Vertex(x, y, z));
		}else if(cmd.equals("f")){
		    int v0 = scn.nextInt();
		    int v1 = scn.nextInt();
		    int v2 = scn.nextInt();

		    faces.add(new Face(vertices.get(v0-1),
				       vertices.get(v1-1),
				       vertices.get(v2-1)));
		}
	    }
	}catch(Exception e){
	    e.printStackTrace();
	    System.exit(1);
	}

	System.out.println("V:"+vertices.size()+"F:"+faces.size());

	for(Vertex v:vertices){
	    v.x /= modelSize;
	    v.y /= modelSize;
	    v.z /= modelSize;
	}
    }

    private void drawModel(Graphics g) {
	g.setColor(Color.WHITE);
	g.fillRect(0,0,WIDTH,HEIGHT);

	for(Face face:faces){
	    int[] px = new int[3];
	    int[] py = new int[3];

	    for(int i=0;i<3;i++){
                px[i] = (int)(center.x + face.v[i].rx * scale);
                py[i] = (int)(center.y - face.v[i].ry * scale);
	    }

	    g.setColor(Color.getHSBColor((float)0.4, (float)0.5, (float)face.nz));
	    g.fillPolygon(px, py, 3);

	    g.setColor(Color.BLACK);
	    g.drawPolygon(px, py, 3);
	}
    }

    private double max(double... args){
	double result = args[0];
	for(int i=1;i<args.length;i++){
	    result = (result < args[i])? args[i]:result;
	}
	return result;
    }
}

class Vertex {
    public double x,y,z;
    public double rx,ry,rz;
   
    public Vertex(double x,double y,double z){
	this.x = x;
	this.y = y;
	this.z = z;
    }
}

class Face {
    public Vertex[] v = new Vertex[3];
    public double nx,ny,nz;
    public double z;  // depth

    public Face(Vertex v0,Vertex v1,Vertex v2){
	v[0] = v0;
	v[1] = v1;
	v[2] = v2;
    }
}