This is code for a prototype app to draw bsplines. Lots of it will be

able to be directly reused in the continuous motion modifications to the
tracker.

robots/tracker/DrawPanel.java

+import java.awt.*;
+import java.awt.geom.*;
+import java.util.*;
+
+
+public class DrawPanel extends javax.swing.JPanel {
+    
+    public static int TOOL_NONE = 0;
+    public static int TOOL_DRAW_SPLINE = 2;
+    public static int TOOL_EDIT_SPLINE = 4;
+    public static int TOOL_DELETE_SPLINE = 8;
+    
+    private Vector splines;
+    private BSpline currentEdit;
+    private int tool;
+    
+    /** Creates new form DrawPanel */
+    public DrawPanel() {
+        initComponents();
+        
+        splines = new Vector();
+        currentEdit = null;
+        
+//        BSpline bs = new BSpline(3, 2, 10, 0.07);
+//        Point p[] = new Point[4];
+//        p[0] = new Point(50,200);
+//        p[1] = new Point(120,100);
+//        p[2] = new Point(180,100);
+//        p[3] = new Point(250,200);
+//        try {
+//            bs.addSegment(p);
+//        }
+//        catch (Exception e) {
+//            e.printStackTrace();
+//        }
+        
+        int xshift = 0;
+        
+        BSpline bs2 = new BSpline(5, BSpline.CONTINUITY_C2, 10, 0.07);
+        Point p2[] = new Point[6];
+        p2[0] = new Point(xshift+50,200);
+         p2[1] = new Point(xshift+85,150);
+        p2[2] = new Point(xshift+120,100);
+        p2[3] = new Point(xshift+180,100);
+         p2[4] = new Point(xshift+215,150);
+        p2[5] = new Point(xshift+250,200);
+        try {
+            bs2.addSegment(p2);
+        }
+        catch (Exception e) {
+            e.printStackTrace();
+        }
+        
+        
+        
+        xshift = 200;
+        
+        //bs2 = new BSpline(5, 2, 10, 0.08);
+        Point p3[] = new Point[6];
+        p3[0] = new Point(xshift+50,200);
+         p3[1] = new Point(xshift+85,150);
+        p3[2] = new Point(xshift+120,100);
+        p3[3] = new Point(xshift+180,100);
+         p3[4] = new Point(xshift+215,150);
+        p3[5] = new Point(xshift+250,200);
+        try {
+            bs2.addSegment(p3);
+        }
+        catch (Exception e) {
+            e.printStackTrace();
+        }
+        
+        //this.addSpline(bs);
+        this.addSpline(bs2);
+    }
+    
+    /** This method is called from within the constructor to
+     * initialize the form.
+     * WARNING: Do NOT modify this code. The content of this method is
+     * always regenerated by the Form Editor.
+     */
+    // <editor-fold defaultstate="collapsed" desc=" Generated Code ">//GEN-BEGIN:initComponents
+    private void initComponents() {
+
+        setLayout(new java.awt.BorderLayout());
+
+        setBackground(new java.awt.Color(255, 255, 255));
+        setPreferredSize(new java.awt.Dimension(250, 200));
+        addMouseMotionListener(new java.awt.event.MouseMotionAdapter() {
+            public void mouseDragged(java.awt.event.MouseEvent evt) {
+                panelMouseDragged(evt);
+            }
+            public void mouseMoved(java.awt.event.MouseEvent evt) {
+                panelMouseMoved(evt);
+            }
+        });
+        addMouseListener(new java.awt.event.MouseAdapter() {
+            public void mouseClicked(java.awt.event.MouseEvent evt) {
+                panelMouseClicked(evt);
+            }
+            public void mousePressed(java.awt.event.MouseEvent evt) {
+                panelMousePressed(evt);
+            }
+            public void mouseReleased(java.awt.event.MouseEvent evt) {
+                panelMouseReleased(evt);
+            }
+        });
+
+    }
+    // </editor-fold>//GEN-END:initComponents
+
+    private int drag_start_x;
+    private int drag_start_y;
+    private BSpline drag_spline;
+    
+    private void panelMouseReleased(java.awt.event.MouseEvent evt) {//GEN-FIRST:event_panelMouseReleased
+        // TODO add your handling code here:
+    }//GEN-LAST:event_panelMouseReleased
+
+    private void panelMousePressed(java.awt.event.MouseEvent evt) {//GEN-FIRST:event_panelMousePressed
+        if (tool == TOOL_EDIT_SPLINE) {
+            drag_start_x = evt.getX();
+            drag_start_y = evt.getY();
+            
+            for (Enumeration e1 = splines.elements(); e1.hasMoreElements(); ) {
+                BSpline bs = (BSpline)e1.nextElement();
+                if (bs.notifyMouseClick(evt.getX(),evt.getY())) {
+                    drag_spline = bs;
+                    this.repaint();
+                    break;
+                }
+            }
+        }
+        
+    }//GEN-LAST:event_panelMousePressed
+
+    private void panelMouseDragged(java.awt.event.MouseEvent evt) {//GEN-FIRST:event_panelMouseDragged
+        if (tool == TOOL_EDIT_SPLINE) {
+            if ( drag_spline != null && 
+                 drag_spline.notifyDrag(evt.getX()-drag_start_x,evt.getY()-drag_start_y) ) {
+                this.repaint();
+            }
+        }
+    }//GEN-LAST:event_panelMouseDragged
+
+    private void panelMouseClicked(java.awt.event.MouseEvent evt) {//GEN-FIRST:event_panelMouseClicked
+        if (tool == TOOL_EDIT_SPLINE) {
+            for (Enumeration e1 = splines.elements(); e1.hasMoreElements(); ) {
+                BSpline bs = (BSpline)e1.nextElement();
+                if (bs.notifyMouseClick(evt.getX(),evt.getY())) {
+                    this.repaint();
+                }
+            }
+        }
+        else if (tool == TOOL_DRAW_SPLINE) {
+            ;
+        }
+        else if (tool == TOOL_DELETE_SPLINE) {
+            for (Enumeration e1 = splines.elements(); e1.hasMoreElements(); ) {
+                BSpline bs = (BSpline)e1.nextElement();
+                if (bs.notifyMouseClick(evt.getX(),evt.getY())) {
+                    splines.remove(bs);
+                    this.repaint();
+                }
+            }
+        }
+    }//GEN-LAST:event_panelMouseClicked
+
+    private void panelMouseMoved(java.awt.event.MouseEvent evt) {//GEN-FIRST:event_panelMouseMoved
+        if (tool == TOOL_EDIT_SPLINE) {
+            for (Enumeration e1 = splines.elements(); e1.hasMoreElements(); ) {
+                BSpline bs = (BSpline)e1.nextElement();
+                if (bs.notifyMouseMotion(evt.getX(),evt.getY())) {
+                    this.repaint();
+                }
+            }
+        }
+    }//GEN-LAST:event_panelMouseMoved
+    
+    public void setTool(int tool) {
+        for (Enumeration e1 = splines.elements(); e1.hasMoreElements(); ) {
+            BSpline bs = (BSpline)e1.nextElement();
+            bs.clearSelection();
+            this.repaint();
+        }
+        
+        this.repaint();
+        
+        if (this.tool == TOOL_DRAW_SPLINE) {
+            // finalize the draw:
+            
+        }
+        
+        this.tool = tool;
+    }
+    
+    public void addSpline(BSpline bs) {
+        splines.add(bs);
+    }
+    
+    protected void paintComponent(Graphics g) {
+        Graphics2D g2 = (Graphics2D)g;
+        
+        if (isOpaque()) { //paint background
+            g2.setColor(getBackground());
+            g2.fillRect(0, 0, getWidth(), getHeight());
+        }
+        g2.addRenderingHints(new RenderingHints(RenderingHints.KEY_ANTIALIASING,
+                                                RenderingHints.VALUE_ANTIALIAS_ON));
+
+        
+        for (Enumeration e1 = splines.elements(); e1.hasMoreElements(); ) {
+            BSpline bs = (BSpline)e1.nextElement();
+            bs.draw(g2,true,true);
+        }
+        
+        // now, if necessary, draw the spline being modified!
+        // maybe only draw the segments that can move...
+        if (currentEdit != null) {
+            currentEdit.draw(g2,false,false);
+        }
+        
+        g2.dispose();
+    }
+    
+    public Dimension getPreferredSize() {
+        return new Dimension(1000,500);
+    }
+    
+    // Variables declaration - do not modify//GEN-BEGIN:variables
+    // End of variables declaration//GEN-END:variables
+    
+}

robots/tracker/Editor.java

+import java.util.*;
+
+
+public class Editor extends javax.swing.JFrame {
+    
+    /** Creates new form Editor */
+    public Editor() {
+        initComponents();
+    }
+    
+    /** This method is called from within the constructor to
+     * initialize the form.
+     * WARNING: Do NOT modify this code. The content of this method is
+     * always regenerated by the Form Editor.
+     */
+    // <editor-fold defaultstate="collapsed" desc=" Generated Code ">//GEN-BEGIN:initComponents
+    private void initComponents() {
+        java.awt.GridBagConstraints gridBagConstraints;
+
+        controlPanel = new javax.swing.JPanel();
+        newSplineButton = new javax.swing.JButton();
+        editSpline = new javax.swing.JButton();
+        deleteSplineButton = new javax.swing.JButton();
+        drawPanel = new DrawPanel();
+
+        getContentPane().setLayout(new java.awt.GridBagLayout());
+
+        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
+        controlPanel.setLayout(new java.awt.GridBagLayout());
+
+        newSplineButton.setText("Add Spline");
+        newSplineButton.addActionListener(new java.awt.event.ActionListener() {
+            public void actionPerformed(java.awt.event.ActionEvent evt) {
+                newSplineButtonActionPerformed(evt);
+            }
+        });
+
+        gridBagConstraints = new java.awt.GridBagConstraints();
+        gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL;
+        gridBagConstraints.anchor = java.awt.GridBagConstraints.NORTH;
+        gridBagConstraints.weightx = 1.0;
+        gridBagConstraints.weighty = 1.0;
+        gridBagConstraints.insets = new java.awt.Insets(2, 2, 2, 2);
+        controlPanel.add(newSplineButton, gridBagConstraints);
+
+        editSpline.setText("Edit Spline");
+        editSpline.addActionListener(new java.awt.event.ActionListener() {
+            public void actionPerformed(java.awt.event.ActionEvent evt) {
+                editSplineActionPerformed(evt);
+            }
+        });
+
+        gridBagConstraints = new java.awt.GridBagConstraints();
+        gridBagConstraints.gridx = 0;
+        gridBagConstraints.gridy = 1;
+        gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL;
+        gridBagConstraints.anchor = java.awt.GridBagConstraints.NORTH;
+        gridBagConstraints.insets = new java.awt.Insets(2, 2, 2, 2);
+        controlPanel.add(editSpline, gridBagConstraints);
+
+        deleteSplineButton.setText("Delete Spline");
+        deleteSplineButton.addActionListener(new java.awt.event.ActionListener() {
+            public void actionPerformed(java.awt.event.ActionEvent evt) {
+                deleteSplineButtonActionPerformed(evt);
+            }
+        });
+
+        gridBagConstraints = new java.awt.GridBagConstraints();
+        gridBagConstraints.gridx = 0;
+        gridBagConstraints.gridy = 2;
+        gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL;
+        gridBagConstraints.insets = new java.awt.Insets(2, 2, 2, 2);
+        controlPanel.add(deleteSplineButton, gridBagConstraints);
+
+        gridBagConstraints = new java.awt.GridBagConstraints();
+        gridBagConstraints.anchor = java.awt.GridBagConstraints.NORTH;
+        gridBagConstraints.weighty = 1.0;
+        gridBagConstraints.insets = new java.awt.Insets(1, 1, 1, 1);
+        getContentPane().add(controlPanel, gridBagConstraints);
+
+        gridBagConstraints = new java.awt.GridBagConstraints();
+        gridBagConstraints.gridx = 1;
+        gridBagConstraints.gridy = 0;
+        gridBagConstraints.fill = java.awt.GridBagConstraints.BOTH;
+        gridBagConstraints.anchor = java.awt.GridBagConstraints.WEST;
+        gridBagConstraints.weightx = 1.0;
+        gridBagConstraints.weighty = 1.0;
+        gridBagConstraints.insets = new java.awt.Insets(1, 1, 1, 1);
+        getContentPane().add(drawPanel, gridBagConstraints);
+
+        pack();
+    }
+    // </editor-fold>//GEN-END:initComponents
+
+    private void deleteSplineButtonActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_deleteSplineButtonActionPerformed
+        drawPanel.setTool(DrawPanel.TOOL_DELETE_SPLINE);
+    }//GEN-LAST:event_deleteSplineButtonActionPerformed
+
+    private void editSplineActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_editSplineActionPerformed
+        drawPanel.setTool(DrawPanel.TOOL_EDIT_SPLINE);
+    }//GEN-LAST:event_editSplineActionPerformed
+
+    private void newSplineButtonActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_newSplineButtonActionPerformed
+        drawPanel.setTool(DrawPanel.TOOL_DRAW_SPLINE);
+    }//GEN-LAST:event_newSplineButtonActionPerformed
+        
+    /**
+     * @param args the command line arguments
+     */
+    public static void main(String args[]) {
+        java.awt.EventQueue.invokeLater(new Runnable() {
+            public void run() {
+                new Editor().setVisible(true);
+            }
+        });
+    }
+    
+    // Variables declaration - do not modify//GEN-BEGIN:variables
+    private javax.swing.JPanel controlPanel;
+    private javax.swing.JButton deleteSplineButton;
+    private DrawPanel drawPanel;
+    private javax.swing.JButton editSpline;
+    private javax.swing.JButton newSplineButton;
+    // End of variables declaration//GEN-END:variables
+    
+}