anchor.diff:  
           List points = [];
   
  -        // X
           points.addAll([xmin, ymin, zmin]);
           points.addAll([xmax, ymin, zmin]);
           points.addAll([xmin, ymax, zmin]);
  
positive.code: 
  
      static PointCloud makeOldCube() {
          Map<String, Float32List> map = new Map();
  
          var numPoints = 24;
  
          var xx = new Float32List(numPoints);
          var yy = new Float32List(numPoints);
          var zz = new Float32List(numPoints);
          map["positions.x"] = xx;
          map["positions.y"] = yy;
          map["positions.z"] = zz;
  
          double xmin = 0.0;
          double xmax = 500.0;
          double ymin = 0.0;
          double ymax = 1000.0;
          double zmin = 0.0;
          double zmax = 1500.0;
  
          // x = red
          // y = green
  
negative.code:         points.addAll([xmin, ymax, zmax]);
          points.addAll([xmax, ymax, zmax]);
  
          points.addAll([xmin + (xmax-xmin)/2, ymin + (ymax-ymin)/2, ymin + (ymax-ymin)/2]);
  
          final int numPoints = points.length ~/ 3;
  
          var xx = new Float32List(numPoints);
          var yy = new Float32List(numPoints);
          var zz = new Float32List(numPoints);
  
          for (int i = 0; i < numPoints; i++) {
              xx[i] = points[i * 3];
              yy[i] = points[i * 3 + 1];
              zz[i] = points[i * 3 + 2];
          }
  
          Map<String, Float32List> map = new Map();
          map["positions.x"] = xx;
          map["positions.y"] = yy;
          map["positions.z"] = zz;
  
          var cloud = new PointCloud("oldcube");
          cloud.addDimensions(map);
  