/* Hidden curve removal          by T.N '97 7/17
	class Point3;   // 頂点の３次元座標
	class Trans;    // 座標変換
*/
import java.applet.Applet;
import java.awt.*;
//import java.io.*;

/* **************************************************************: */
public class hidfunc extends java.applet.Applet{
	int width, height;
 	int x_origin,y_origin;             //center of screem
	double theta=70., phi=20., R=800.; // 視点位置
    int idrag=0;
	Point prev = new Point(0, 0);
	Trans henkan = new Trans();

/* **************************************************************: */
    public void init() {

		setBackground(Color.lightGray);
		Dimension appsize = size();
		width = appsize.width;  // for JDK1.1
		height = appsize.height;

//		width = getSize().width; // for JDK1.2
//		height = getSize().height;

	    x_origin = width/2;
		y_origin = height/2;

        henkan.setVRpnt(0.,0.,0.);      // set view refrence point
        henkan.setview(R,theta,phi);    // set viewpoint
   }
/* *************** 描画関数 *****************************: */
    public void paint(Graphics g) {
	 int px,py;
	 int ymin[] = new int[width];
	 int ymax[] = new int[width];

	 g.setColor(Color.black);
	 henkan.preper();         // 座標変換の係数セット

	 for(int i=0;i<width;i++){    // 初期化
		 ymin[i]=height; ymax[i]=0;}

	 int dz=10; int dx=1;
	 if(idrag==1) {dz=40; dx=8;}

	 // ｚ、ｘを変化させて、ｙ= f(z,x) を 計算
	 for(int z=170;z>=-170;z=z-dz){
		 for(int x=-170;x<=170;x=x+dx){
			 Point3 P = FuncHat(x,z);     // 関数生成 P(x,y,z)
			 Point q = henkan.project(P); // 透視投影 q(x,y)
			 px = x_origin + q.x ;   py =  y_origin - q.y;
			if(px>0 && px<width){
			if(py<ymin[px]) { ymin[px]=py;
				 g.drawLine(px,py, px, py); }
			 if(py>ymax[px]){	 ymax[px]=py;
				 g.drawLine(px,py, px,py); }
			}
		 } // loop for x
	 } // loop for z
	}
/* ************** Function z = F(x,y) *******************: */
	public Point3 FuncHat(int x,int y) {
		double rd= Math.PI/180;

		double r = Math.sqrt(x*x+y*y)*rd;
		double z=30.*(Math.cos(r)+Math.cos(3.*r));
       return new Point3(x,y,z);
	}

/* **************************************************************: */
	public boolean mouseDown(Event evt, int x, int y) {
		prev = new Point(x, y);
		repaint();
		return true;
    }
// ------------------------------------------------------------------
	public boolean mouseDrag(Event ev, int x, int y) {

		  int ia,ib;
		  ia = x-prev.x; ib=y-prev.y;
		  if(ia>8 || ia<-8 || ib>8 || ib<-8) { 
			idrag=1;
		    theta += ia/2;  phi -= ib/2;
            henkan.setview(R,theta,phi); 
		  }  else idrag=0;
		repaint();
		prev.move(x, y);
		return true;
	}
// ------------------------------------------------------------------
	public boolean mouseUp(Event ev, int x, int y) {
		prev = null;
        idrag=0;
		return true;
	}
}

// --  Class for perspective transformation ---------
class Trans {
	double  cos_theta=1., cos_phi=1., sin_theta=0., sin_phi=0.;
	Point3 ptViewRef = new Point3(0, 0, 0);   // view reference point
	double theta, phi, R;

	Trans() {
	}
  public void setVRpnt( double x, double y, double z) {
     ptViewRef = new Point3(x,y,z);
  }
  public void setview(double r, double the, double ph) {
     theta=the; phi=ph; R=r;
  }

//     perspective transformation  
  public void preper() {
		double d2r= Math.PI/180;

		cos_theta = Math.cos(theta*d2r);
		sin_theta = Math.sin(theta*d2r);
		cos_phi = Math.cos(phi*d2r);
		sin_phi = Math.sin(phi*d2r);
	}
//  Transforms world coordinate-system to viewpoint coordinate-system.
	public Point3 tranfrm(Point3 point) {
		Point3 p1 = new Point3();
		Point3 p2 = new Point3();

		p1.x = point.x - ptViewRef.x;
		p1.y = point.y - ptViewRef.y;
		p1.z = point.z - ptViewRef.z;

    	double xy = cos_theta*p1.x+sin_theta*p1.y; 	
		p2.z =(R-cos_phi*xy-sin_phi*p1.z)/R;
	    p2.x = cos_theta*p1.y-sin_theta*p1.x;	
		p2.y = cos_phi * p1.z - sin_phi * xy;

		return p2;
	}
	public Point project(Point3 point) {
		Point3 p1= tranfrm(point);
		return new Point((int)(p1.x/p1.z), (int)(p1.y/p1.z)); 
	}
}

//    3D real point class 
class Point3 {
	public double x, y, z;

	Point3() {
	}

	Point3(double ox, double oy, double oz) {
	x = ox; y = oy; z = oz;
	}
}