[patch] Use a multiplier instead of a fixed "createcircle.nodecount"

[Atalanttore]

Hi,

I would prefer a multiplier instead of a fixed createcircle.nodecount with a default value of 16. Big circles often need more nodes than 16 and small ones probably less than 16.

My idea is to calculate the necessary nodecount of the circle depending on the distance between the two or three selected nodes for creating a circle.

In short: distance between the selected nodes * multiplier = nodecount

Best Regards,
Ettore Atalan

[simon04]

Ticket #12475 has been marked as a duplicate of this ticket.

[naoliv]

Empirically I tested the radius value with a (what I consider to be a) satisfactory number of nodes:

r  → n
2  → 8
4  → 12
8  → 16
16 → 24
32 → 32
64 → 48

ie, a radius of 16 meters should give us 24 nodes in the circle.

And found a formula that gives a good approximation for this, as 6 * r ^ (1/2)

Of course you will ignore that I don't know Java and consider this as a proof of concept, but I got some very good results by using

numberOfNodesInCircle = (int) Math.ceil(6.0 * Math.pow(r, 0.5));

right after the radius is calculated (at https://josm.openstreetmap.de/browser/josm/trunk/src/org/openstreetmap/josm/actions/CreateCircleAction.java#L195)

Is it possible to properly implement this?

[Atalanttore]

Thanks for working on my suggestion.

[naoliv]

Functional proof-of-concept patch:

src/org/openstreetmap/josm/actions/CreateCircleAction.java

@@ -130 +130 @@
         if (!isEnabled())
             return;
 
-        int numberOfNodesInCircle = Main.pref.getInteger("createcircle.nodecount", 16);
-        if (numberOfNodesInCircle < 1) {
-            numberOfNodesInCircle = 1;
-        } else if (numberOfNodesInCircle > 100) {
-            numberOfNodesInCircle = 100;
-        }
-
         DataSet ds = getLayerManager().getEditDataSet();
         Collection<OsmPrimitive> sel = ds.getSelected();
         List<Node> nodes = OsmPrimitive.getFilteredList(sel, Node.class);
@@ -193 +186 @@
         double r = Math.sqrt(Math.pow(center.east()-n1.east(), 2) +
                 Math.pow(center.north()-n1.north(), 2));
 
+        // minimum circle will have 6 nodes when using a way with length ≥ 1.4m
+        if (r < 0.7) {
+            new Notification(
+                tr("Nodes are too close to create a circle."))
+                .setIcon(JOptionPane.INFORMATION_MESSAGE)
+                .setDuration(Notification.TIME_LONG)
+                .show();
+            return;
+        }
+
+        // see #10777
+        int numberOfNodesInCircle = (int) Math.ceil(6.0 * Math.pow(r, 0.5));
+
         // Order nodes by angle
         PolarNode[] angles = new PolarNode[nodes.size()];
         for (int i = 0; i < nodes.size(); i++) {

My view: we don't need to have a default value anymore (since it's dynamically calculated using the radius) nor we should create too tiny circles.

[bastiK]

Thanks for the patch! Just two remarks:

• The variable r is not in meter. To get a value in meter, you can use LatLon.greatCircleDistance.
• This is a matter of taste, but why not just take a minimum of 6 points, instead of refusing to create a small circle?

[naoliv]

New version:

src/org/openstreetmap/josm/actions/CreateCircleAction.java

@@ -130 +130 @@
         if (!isEnabled())
             return;
 
-        int numberOfNodesInCircle = Main.pref.getInteger("createcircle.nodecount", 16);
-        if (numberOfNodesInCircle < 1) {
-            numberOfNodesInCircle = 1;
-        } else if (numberOfNodesInCircle > 100) {
-            numberOfNodesInCircle = 100;
-        }
-
         DataSet ds = getLayerManager().getEditDataSet();
         Collection<OsmPrimitive> sel = ds.getSelected();
         List<Node> nodes = OsmPrimitive.getFilteredList(sel, Node.class);
@@ -193 +186 @@
         double r = Math.sqrt(Math.pow(center.east()-n1.east(), 2) +
                 Math.pow(center.north()-n1.north(), 2));
 
+        // see #10777
+        LatLon ll1 = Main.getProjection().eastNorth2latlon(n1);
+        LatLon ll2 = Main.getProjection().eastNorth2latlon(center);
+
+        double radiusInMeters = ll1.greatCircleDistance(ll2);
+
+        int numberOfNodesInCircle = (int) Math.ceil(6.0 * Math.pow(radiusInMeters, 0.5));
+        if (numberOfNodesInCircle < 6) {
+            numberOfNodesInCircle = 6;
+        }
+
         // Order nodes by angle
         PolarNode[] angles = new PolarNode[nodes.size()];
         for (int i = 0; i < nodes.size(); i++) {

[bastiK]

In 12837/josm:

fixed #10777 - new algorithm to determine the node count in CreateCircleAction (patch by naoliv)

[bastiK]

Thanks for the patch, your square root formula works quite well!

[naoliv]

Great! Thank you!

[Don-vip]

Ticket #15350 has been marked as a duplicate of this ticket.

[ika-chan! on OpenStreetMap]

Hi, I wonder if this can be enhanced further to still allow me to dictate the exact number of nodes? I use JOSM to do some local map experiments, but in some cases I wanted to create a circle an exact number of nodes (e.g. 360 or 720). Thanks in advance.

[Klumbumbus]

You could:

• create a circle at the radius that gives you approxiamtely 360 nodes
• manually delete or add a few nods to match exactly 360
• press O to make it a circle again
• resize it (ctrl + alt + mouse move)

[ika-chan! on OpenStreetMap]

Hi Klumbumbus, with all due respect I have a obsession with accuracy. How would the change allow me to ensure that the radius is of an exact value (e.g. 5 km or 10 km)? I like the new way of creating circles, but I also like an advanced mode for exact values. ;-)

[naoliv]

@ika-chan
Install ​https://wiki.openstreetmap.org/wiki/JOSM/Plugins/CommandLine and modify the example circle.xml to allow a higher value in maxvalue (ie, instead maxvalue="144" you can set maxvalue="1024")

You will be able to specify exactly the radius and number of nodes that you want.