// Modification history // Nov. 3, impletemt double buffering //----------------------------------------------------- // written by Fu-Kwun Hwang // Last modified date: Oct. 30, 1996 // I hope that you enjoy this applet // Suggestions? Send E-mail to hwang@phy03.phy.ntnu.edu.tw //----------------------------------------------------- import java.awt.*; public class startButton extends java.applet.Applet{ String buttonText="start"; String windowTitle="Thin Lens demonstration by Fu-Kwun Hwang"; int windowWidth = 600; int windowHeight = 300; MainWindow m; int windowCount=0; public void init() { String str; // get parameters if((str=getParameter("buttonText"))!=null) buttonText=str; if((str=getParameter("windowTitle"))!=null) windowTitle=str; if((str=getParameter("windowWidth"))!=null) windowWidth=Integer.parseInt(str); if((str=getParameter("windowHeight"))!=null) windowHeight=Integer.parseInt(str); if((str=getParameter("autoStart"))!=null){ m = new MainWindow(windowTitle, true); go(); } add(new Button("Start")); } private void go(){ m.resize(windowWidth,windowHeight); m.show(); m.start(); } public boolean action(Event e,Object arg) { if (e.target instanceof Button && ((String)arg).equals(buttonText)) { m = new MainWindow(String.valueOf(++windowCount)+":"+ windowTitle, true); } go(); return true; } //These methods allow the applet to // also run as an application. public static void main(String args[]) { new startButton().begin(); } private void begin() { m = new MainWindow(windowTitle, false); go(); } } class MainWindow extends Frame { boolean is_applet; Animation anim; MainWindow(String title, boolean isapp){ super(title); is_applet=isapp; anim=new Animation(this); add("Center",anim); setBackground(Color.white); } public void start(){ anim.reset(); repaint(); } public boolean handleEvent(Event e) { if (e.id == Event.WINDOW_DESTROY) { hide(); removeAll(); dispose(); if(!is_applet) System.exit(0); } return super.handleEvent(e); } public void paint(Graphics g){ anim.reset(); anim.repaint(); } } class control extends Panel{ TextField textP,textQ,textF,textM,textR; Button type; Animation anim; control(Animation an){ anim=an; add(textR=new TextField("mouse X,Y",8)); add(new Label("p=")); add(textP=new TextField("40.",5)); add(new Label("q=")); add(textQ=new TextField("40.",5)); add(new Label("f=")); add(type=new Button("+")); add(textF=new TextField("20.",5)); add(new Label("M=")); add(textM=new TextField("1.",5)); } public boolean action(Event ev, Object arg) { String label = (String)arg; if (ev.target instanceof Button) { if(label.equals("+")) type.setLabel("-"); else if(label.equals("-")) type.setLabel("+"); anim.l.f*=-1.; anim.repaint(); return true; }else if( ev.target instanceof TextField){ double value; value=Double.valueOf(label).doubleValue(); if(ev.target==textP) anim.textInput(1,value); else if(ev.target==textQ) anim.textInput(2,value); else if(ev.target==textF) anim.textInput(3,value); else if(ev.target==textM) anim.textInput(4,value); anim.repaint(); return true; } return false; } } class Animation extends Canvas { Thread animatorThread; Dimension area; control p; lens l; int xc,yc; double scale=10.; Animation(MainWindow m){ p=new control(this); m.add("North",p); } public void reset() { area=size(); xc=area.width/2; yc=area.height/2; if(l==null){ double ff=10.*scale; l=new lens(xc,yc,(int)(0.75*yc),ff); p.textF.setText(Double.toString(ff)); }else l.move(xc,yc); xc-=(int)(2.*l.f); // initial object position yc=yc*3/4; } boolean objectmove=false; public boolean mouseDown(Event e, int x, int y){ if(!l.mouseDown(x,y)){ if(Math.abs(x-xc)<5 ){ xc=x; yc=y; repaint(); objectmove=true; } } return true; } public boolean mouseDrag(Event e, int x, int y){ if(l.mouseDrag(x,y)) repaint(); // change lens else if(objectmove){ // move object xc=x; yc=y; writeXY(x,y); repaint(); } return true; } public boolean mouseUp(Event e, int x, int y){ l.mouseUp(x,y); objectmove=false; repaint(); return true; } public boolean mouseMove(Event evt, int x, int y){ if(!objectmove) writeXY(x,y); return true; } private void writeXY(int x, int y){ p.textR.setText( Double.toString((double)(l.xc-x)/scale)+ ", "+ Double.toString((double)(l.yc-y)/scale)); } public boolean mouseExit(Event evt, int x, int y){ p.textR.setText("mouse X,Y"); return true; } public void textInput(int type,double value){ switch (type) { case 1: // P xc=l.xc-(int)(value*scale); break; case 2: // Q xc=l.xc-(int)(1./(1./l.f-1./(scale*value))); break; case 3: // F l.f=value*scale; break; case 4: // M xc=l.xc-(int)(Math.abs((1.-1./value)*l.f)); break; } } Dimension offDimension; Image offImage; Graphics g; public void paint(Graphics gs){ update(gs); } public void update(Graphics gs){ if ( (g == null) || (area.width != offDimension.width) || (area.height != offDimension.height) ) { offDimension = area; offImage = createImage(area.width, area.height); g = offImage.getGraphics(); l.setGraphics(g); } //Erase the previous image. g.setColor(getBackground()); g.fillRect(0, 0, area.width, area.height); g.setColor(Color.black); //public void paint(Graphics g){ g.drawLine(0,area.height/2,area.width,area.height/2); drawGrid(g); drawRay(g); l.show(); gs.drawImage(offImage, 0, 0, this); } private void drawGrid(Graphics g){ g.setColor(Color.gray); int i,j; for(i=l.xc,j=0;i>0;j++,i=l.xc-(int)(j*scale)) g.drawLine(i,l.yc-2,i,l.yc+2); for(i=l.xc,j=0;ixc){ ox=l.xc-xc; side=1; }else{ ox=xc-l.xc; side=-1; } oy=l.yc-yc; ix=1./(1./l.f-1./ox); magnify=-ix/ox; iy=magnify*oy; // write P,Q,F writeText(p.textP,Math.abs(l.xc-xc)); writeText(p.textQ,ix); writeText(p.textF,Math.abs(l.f)); writeText(p.textM,magnify*scale); int x1,y1,x2,y2; // ray paths x1=l.xc-side*ox; y1=l.yc-oy; x2=l.xc+side*(int)ix; y2=l.yc-(int)iy; //draw object drawit(g,x1,l.yc,oy); g.setColor(Color.blue); g.drawLine(x1,y1,l.xc,y1); //1-1 if(magnify<0){ g.drawLine(l.xc,y1,x2,y2); //1-2 g.drawLine(x1,y1,x2,y2); //2 g.drawLine(x1,y1,l.xc,y2); //3-1 g.drawLine(l.xc,y2,x2,y2); //3-2 g.setColor(Color.blue); }else{ if(l.f>0){ // converging lens g.drawLine(l.xc,y1,l.xc+2*side*(int)l.f,l.yc+oy); //1-2 g.drawLine(x1,y1,l.xc-side*(int)ix,l.yc+(int)iy); //2-1 g.drawLine(x1,y1,l.xc,l.yc-(int)iy); //3-1 g.drawLine(l.xc,y2,l.xc+2*side*(int)l.f,y2); //3-2 g.setColor(Color.green); g.drawLine(x1,y1,x2,y2); //2-2 g.drawLine(l.xc,y1,x2,y2); //1-3 g.drawLine(l.xc,y2,x2,y2); }else{ // diverging lens g.drawLine(l.xc,y1,l.xc-2*side*(int)l.f,l.yc-3*oy); //1-2 g.drawLine(x1,y1,l.xc+side*ox,l.yc+(int)oy); //2 g.drawLine(x1,y1,l.xc,y2); //3-1 g.drawLine(l.xc,y2,l.xc-2*side*(int)l.f,y2); //3-2 g.setColor(Color.green); g.drawLine(l.xc,y1,l.xc+side*(int)l.f,l.yc); //1-3 g.drawLine(l.xc,y2,l.xc+side*(int)ix,y2); //3-3 } } drawit(g,x2,l.yc,(int)iy); // draw image } private void drawit(Graphics g,int x,int y,int height){ // for object and image int x1,y1,width=4,sign=1; x1=x-width/2; if(height<0){ sign=-1; y1=y; }else y1=y-height; g.fillRect(x1,y1,width,sign*height); y1=y-height; width=2*width; sign*=2; // draw hats g.drawLine(x,y1,x+width,y1+sign*width); g.drawLine(x,y1,x-width,y1+sign*width); } } class lens{ int xc,yc,h; // (xc,yc):center position, h:height of lens double r,f; // focusLength*2; int width; // half/quater width of lens Graphics g; lens(int x,int y,int hi, double fi){ //g=gs; init(x,y,hi,fi); } private void init(int x, int y,int hi,double fi){ xc=x; yc=y; r=Math.abs(2.*fi); f=fi; if(hi<10)h=10; // minimum height of lens else h=hi; } private void set(int x, int y,int hi,double fi){ init(x,y,hi,fi); show(); } public void setGraphics(Graphics gs) {g=gs;} // for netscape 3.0 only, fixed clip-region problem // when window enlarged boolean moving=false; boolean sizing=false; boolean mouseDown(int x,int y){ if(Math.abs(x-xc)