How to assemble an array(s) of continuous points f

Question

I have a Conrec nightmare. I am trying to implement contour lines in ActionScript using Conrec. I have looked at both the java and javascript implementation and am still stuck. These are found here: http://paulbourke.net/papers/conrec/

Conrec will take grid data and assemble continuous contour lines. The problem is that it does not necessarily draw those lines in a continuous fashion. For example, it will draw A->B and then C->B and then C->D instead of A, B, C, D, etc.

The javascript implementation seems to be accounting for this and serializing the instructions into an array of draw points. Which is what I too want to accomplish in the end. That is it takes the instructions from the core Conrec logic (eg: A->B, C->B, C->D, etc) and organizes it into an A, B, C, D series. I think it will also return the series as a multi-dimensional array to accommodate broken lines (eg: [[A, B, C, D], [E, F, G]]). This last functionality is what I need to do in Actionscript.

This last part is where I am stuck. Ignore Conrec for now (I have given up on finding an Actionscript implementation), how can I organize these instructions into a collection of serial points? When Conrec gives me "draw point from X->Y" how can I first check if X or Y are already in a series and append either X or Y (whichever is not in the series) into the series? AND if neither are in the series, start a NEW series with X, Y as the starting set. Then check subsequent instructions against all existing series and connect series if they now start and stop on the same point? Also, I need to be able to allow for a series to close itself (eg: A, B, C, A) -- a loop (is that even possible?!).

I hope this makes sense. I'm not sure if there is a technical term for what I want to do beyond "concatenation". I also hope someone out there has done this with Conrec and can give me some pointers.

In the meantime, I am going to continue to plug away at this and see if I can come up with something but I am not confident in my abilities. I would really be thankful for some veteran or professional advice.

PS: If you know another way to draw contour lines from grid data, I am open to alternatives. But I have to be able to implement it in Actionscript.

Answer 1

I just ported ConRec to Actionscript3 and seems to work fine, I haven't tested it thoroughly, but it draws my contours the way I expect. Try it out if you will, I'm curious if it's a correct port. it's here:

http://www.jvanderspek.com/DEV/ConRec/ConRec.as

Answer 2

Ok, here is my first attempt at getting what I need done. I am not terribly happy with the result, but it seems to work.

package {
  import flash.display.Sprite;

  public class lineSeriesPointConcat extends Sprite {
    public function lineSeriesPointConcat() {
      init();
    }
    //directions [X -> Y]
    //case 1: both counterclockwise, result is counterclockwise
    private var case1:Array = [
      ["G1", "F1"], 
      ["F1", "E1"], 

      ["D1", "C1"],
      ["C1", "B1"],
      ["B1", "A1"], 

      ["E1", "D1"], //link
      ["G1", "A1"] //loop
    ];

    //case 2: clockwise, counterclockwise, result is clockwise
    private var case2:Array = [
      ["E2", "F2"], 
      ["F2", "G2"], 

      ["D2", "C2"], 
      ["C2", "B2"], 
      ["B2", "A2"], 

      ["E2", "D2"], //link
      ["G2", "A2"] //loop
    ];

    //case 3: both clockwise, result is clockwise
    private var case3:Array = [
      ["E3", "F3"], 
      ["F3", "G3"], 

      ["A3", "B3"], 
      ["B3", "C3"], 
      ["C3", "D3"], 

      ["E3", "D3"], //link
      ["G3", "A3"] //loop
    ];

    //case 4: counterclockwise, clockwise, result is clockwise
    private var case4:Array = [
      ["G4", "F4"], 
      ["F4", "E4"], 

      ["A4", "B4"], 
      ["B4", "C4"], 
      ["C4", "D4"], 

      ["E4", "D4"], //link
      ["G4", "A4"] //loop
    ];


    private var collectedSeries:Array = [];

    private function init():void {
      var directions:Array = case1.concat(case2.concat(case3.concat(case4)));
      for each (var direction:Array in directions) {
        connect(direction[0], direction[1]);
      }
      trace ("final series:\n\t" + collectedSeries.join("\n\t"));
    }

    private function connect(from:String, to:String):void {
      var series:Array;
      var seriesStart:String;
      var seriesEnd:String;
      var seriesIndex:int;
      var n:int = collectedSeries.length;
      var i:int;
      for (i = 0; i < n; i++) {
        series = collectedSeries[i];
        seriesStart = series[0];
        seriesEnd = series[series.length - 1];

        if (seriesStart == to) {
          seriesStart = from;
          series.unshift(from);
          break;
        } else if (seriesStart == from) {
          seriesStart = to;
          series.unshift(to);
          break;
        } else if (seriesEnd == to) {
          seriesEnd = from;
          series.push(from);
          break;
        } else if (seriesEnd == from) {
          seriesEnd = to;
          series.push(to);
          break;
        }
      }

      if (i == n) {
        //this is a new series segment
        series = [from, to];
        seriesStart = from;
        seriesEnd = to;
        collectedSeries.push(series);
      }

      for (var j:int = 0; j < n; j++) {
        var compareSeries:Array = collectedSeries[j];
        if (compareSeries == series) {
          //don't compare the series to itself.
          continue;
        }
        var compSeriesStart:String = compareSeries[0];
        var compSeriesEnd:String = compareSeries[compareSeries.length - 1];
        if (compSeriesStart == compSeriesEnd) { 
          //this series loops on itself, it will not concatenate further
          continue;
        }
        if (compSeriesStart == seriesEnd) {
          trace ("case 1");
          series = series.concat(compareSeries.slice(1));
        } else if (compSeriesStart == seriesStart) {
          trace ("case 2");
          series = compareSeries.reverse().concat(series.slice(1));
        } else if (compSeriesEnd == seriesStart) {
          trace ("case 3");
          series = compareSeries.concat(series.slice(1));
        } else if (compSeriesEnd == seriesEnd) {
          trace ("case 4");
          series = compareSeries.concat(series.reverse().slice(1));
        } else {
          //no linkage between these two series
          continue;
        }
        collectedSeries[i] = series; //replace one of the two segements
        collectedSeries.splice(j, 1); //splice out the other
        break;
      }
      trace ("series: " + series + (i == n ? " new" : ""));
    }
  }
}

This will give the following results:

A1,G1,F1,E1,D1,C1,B1,A1

G2,A2,B2,C2,D2,E2,F2,G2

G3,A3,B3,C3,D3,E3,F3,G3

G4,A4,B4,C4,D4,E4,F4,G4

I would still really appreciate any advice/feedback I can get. Does no one use Conrec?!

Edit: woops! I had a bug with the original splice()! sorry! fixed now

Answer 3

Ok, so there may be a much better alternative for Flash. I just found this link and it looks impressive. If this works, it obviates the original problem...

isolining package for ActionScript 3