Polyspiral

Polyspiral is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

A Polyspiral is a spiral made of multiple line segments, whereby each segment is larger (or smaller) than the previous one by a given amount. Each segment also changes direction at a given angle.

The task: animate a series of polyspirals, by drawing a complete spiral then incrementing the angle, and (after clearing the background) drawing the next, and so on.

WHILE true

    x = width / 2
    y = height / 2
    set length

    FOR 1 TO 150
        drawline
        change direction by angle
        increment length
    ENDFOR

    increment angle MOD 360

If animation is not practical in your programming environment, you may show 3 frames from different stages of the animation instead.

J

Translation of: java

<lang J>require 'gl2 trig media/imagekit' coinsert 'jgl2'

DT =: %30 NB. seconds ANGLE =: 0.025p1 NB. radians DIRECTION=: 0 NB. radians

POLY=: noun define pc poly;pn "Poly Spiral"; minwh 320 320; cc isi isigraph; )

poly_run=: verb define

 wd POLY,'pshow'
 wd 'timer ',":DT * 1000

)

poly_close=: verb define

 wd 'timer 0; pclose'

)

sys_timer_z_=: verb define

 recalcAngle_base_ 
 wd 'psel poly; set isi invalid'

)

poly_isi_paint=: verb define

 drawPolyspiral DIRECTION

)

recalcAngle=: verb define

 DIRECTION=: 2p1 | DIRECTION + ANGLE

)

drawPolyspiral=: verb define

 glclear
 x1y1 =. (glqwh)%2
 a=. -DIRECTION
 len=. 5
 for_i. i.150 do.
   glpen glrgb Hue a % 2p1
   x2y2=. x1y1 + len*(cos,sin) a
   gllines <.x1y1,x2y2
   x1y1=. x2y2
   len=. len+3
   a=. 2p1 | a - DIRECTION
 end.

)

poly_run</lang>

Java

Works with: Java version 8

<lang java>import java.awt.*; import java.awt.event.ActionEvent; import javax.swing.*;

public class PolySpiral extends JPanel {

   double inc = 0;

   public PolySpiral() {
       setPreferredSize(new Dimension(640, 640));
       setBackground(Color.white);

       new Timer(40, (ActionEvent e) -> {
           inc = (inc + 0.05) % 360;
           repaint();
       }).start();
   }

   void drawSpiral(Graphics2D g, int len, double angleIncrement) {

       double x1 = getWidth() / 2;
       double y1 = getHeight() / 2;
       double angle = angleIncrement;

       for (int i = 0; i < 150; i++) {

           g.setColor(Color.getHSBColor(i / 150f, 1.0f, 1.0f));

           double x2 = x1 + Math.cos(angle) * len;
           double y2 = y1 - Math.sin(angle) * len;
           g.drawLine((int) x1, (int) y1, (int) x2, (int) y2);
           x1 = x2;
           y1 = y2;

           len += 3;

           angle = (angle + angleIncrement) % (Math.PI * 2);
       }
   }

   @Override
   public void paintComponent(Graphics gg) {
       super.paintComponent(gg);
       Graphics2D g = (Graphics2D) gg;
       g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
               RenderingHints.VALUE_ANTIALIAS_ON);

       drawSpiral(g, 5, Math.toRadians(inc));
   }

   public static void main(String[] args) {
       SwingUtilities.invokeLater(() -> {
           JFrame f = new JFrame();
           f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
           f.setTitle("PolySpiral");
           f.setResizable(true);
           f.add(new PolySpiral(), BorderLayout.CENTER);
           f.pack();
           f.setLocationRelativeTo(null);
           f.setVisible(true);
       });
   }

}</lang>

zkl

If you click on the image, it is animated.

Uses the PPM class from http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#zkl <lang zkl>w,h:=640,640; bitmap:=PPM(w,h,0xFF|FF|FF); // White background angleIncrement:=(3.0).toRad(); while(True){

  r,angle:=0.0, 0.0;
  ao,len,inc:=w/2, 2.5, angleIncrement+(130.0).toRad();
  foreach c in (128){
     s,a:=r + len, angle + inc;
     x,y:=r.toRectangular(angle);
     u,v:=r.toRectangular(a);
     c=c.shiftLeft(21) + c.shiftLeft(10) + c*8;  // convert c to a RGB
     bitmap.line(ao+x,ao+y, ao+u,ao+v, c);
     r,angle=s,a;
  }
  bitmap.writeJPGFile("polyspiral.zkl.jpg");
  bitmap.fill(0xFF|FF|FF);  // White background
  angleIncrement=(angleIncrement + 0.05);
  Atomic.sleep(3);

}</lang>