Triangulation 2D

Creates a Delaunay triangulation <https://en.wikipedia.org/wiki/Delaunay_triangulation> from a set of 2D points. Then displays the results using Swing.

ExampleMetricLine.java

   public static void main( String[] args ) {

       // Rectangular region points will be randomly put into
       int width = 400, height = 300;

       // border that points won't be place inside of
       int border = 10;

       // Randomly generate points
       var random = new Random(0xF00D);
       var points = new DogArray<>(Point2D_F64::new);
       for (int i = 0; i < 50; i++) {
           // Avoid generating points right on the image edge. This is for appearance only
           double x = border + random.nextDouble()*(width - 2*border);
           double y = border + random.nextDouble()*(height - 2*border);
           points.grow().setTo(x, y);
       }

       // Compute the Delaunay triangulation
       var delaunay = new DelaunayIncrementalWalk();

       // Uncomment below to print debug info to stdout
       // delaunay.setVerbose(System.out, null);

       // To make it more generic a function interface is used for the points array. This avoids making you
       // convert it into a specific array format
       delaunay.process(( idx, p ) -> {
           p.setTo(points.get(idx));
           return true;
       }, points.size);

       // Convert internal results into a standard mesh data structure
       Mesh2D_F64 mesh = delaunay.toMesh(null);

       visualizeWithSwing(width, height, mesh);
   }

   /// Visualize results using Swing. Draws the triangles and points.
   private static void visualizeWithSwing( int width, int height, Mesh2D_F64 mesh ) {
       // Visualize results
       var image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
       Graphics2D g2 = image.createGraphics();

       // Turn on antialiasing so that it looks less like graphics from the 1980s
       g2.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);
       g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

       // White background
       g2.setColor(Color.WHITE);
       g2.fillRect(0, 0, width, height);

       // Draw the triangles
       g2.setStroke(new BasicStroke(2));
       g2.setColor(Color.BLACK);
       var line = new Line2D.Double();
       var triangle = new Triangle2D_F64();
       for (int triangleID = 0; triangleID < mesh.triangles.size; triangleID += 3) {
           mesh.getTriangle(triangleID, triangle);

           for (int i = 0, j = 2; i < 3; j = i, i++) {
               Point2D_F64 a = triangle.get(j);
               Point2D_F64 b = triangle.get(i);
               line.setLine(a.x, a.y, b.x, b.y);
               g2.draw(line);
           }
       }

       // Draw the points
       g2.setColor(Color.RED);
       int r = 5;
       var oval = new Ellipse2D.Double();
       for (int pointID = 0; pointID < mesh.points.size(); pointID++) {
           Point2D_F64 p = mesh.points.getTemp(pointID);
           oval.setFrame(p.x - r, p.y - r, 2*r, 2*r);
           g2.fill(oval);
       }

       var panel = new JPanel() {
           @Override protected void paintComponent( Graphics g ) {
               super.paintComponent(g);
               g.drawImage(image, 0, 0, null);
           }
       };
       panel.setPreferredSize(new Dimension(width + 10, height + 10));

       var frame = new JFrame();
       frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
       frame.add(panel);
       frame.pack();
       frame.setVisible(true);
   }