these are no tangents.

When hitting the circle he spliced and continued on a line from the opposite site randomly chosen....


When hitting the circle = dist of current end of this line to the centerX,centerY < radius
use function dist()

cheers. i know there are no tangents (changed that!)

Here is one example of how to do it...

Code Example

1. PVector origin = new PVector(200, 250);
2. float rad = 125;
3. float lineHeight = 14;
4.  
5. float rp2 = pow(rad,2);
6. ArrayList <PVector> pointsIn = new ArrayList <PVector> ();
7. ArrayList <PVector> pointsOut = new ArrayList <PVector> ();
8.  
9. void setup() {
10.   size(400, 500);
11.   colorMode(HSB, height, 100, 100);
12.   strokeWeight(1.5);
13.   getPoints();
14.   smooth();
15. }
16.  
17. void draw() {
18.   background(0, 0, 100);
19.   for (int y=0; y<height; y+=lineHeight) {
20.     if (y < origin.y - rad || y > origin.y + rad) {
21.       stroke(y, 100, 100);
22.       line(0,y,width,y);
23.     }
24.   }
25.   for (int i=0; i<pointsIn.size(); i++) {
26.     PVector in = pointsIn.get(i);
27.     PVector out = pointsOut.get(i);
28.     stroke(in.y, 100, 100);
29.     line(0, in.y, in.x, in.y);
30.     line(in.x, in.y, out.x, out.y);
31.     line(out.x, out.y, width, out.y);
32.   }
33. }
34.  
35. void mousePressed() {
36.   getPoints();
37. }
38.  
39. void getPoints() {
40.   pointsIn.clear();
41.   pointsOut.clear();
42.   for (int y=0; y<height; y+=lineHeight) {
43.     if (y >= origin.y - rad && y <= origin.y + rad) {
44.       float dx = sqrt(rp2-pow((origin.y-y),2));
45.       PVector in = new PVector(origin.x-dx, y);
46.       PVector out = new PVector(origin.x+dx, y);
47.       pointsIn.add(in);
48.       pointsOut.add(out);
49.     }
50.   }
51.   Collections.shuffle(pointsOut);
52. }

Lovely work thanks (both Chris and Amnon).