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Enumerating Polygon Islands

This example demonstrates how to enumerate polygon islands by implementing a function that returns an array of all the polygon islands, each one as a PolygonFaceCollection.

JScript Example: enumerating polygon islands

function GetIslands(in_obj) 
{
   var arrIslands = new Array();
   var plyPolygons = in_obj.ActivePrimitive.Geometry.Polygons;
   var arrSeen = new Array(plyPolygons.Count); // for optimization

   for ( var i=0; i<plyPolygons.Count; i++ ) {
       // Skip any we've already seen
       if ( arrSeen[i] ) { continue; }

       // Stuff the current polygon into an XSICollection (custom 
       // filters only accept and return XSICollections)
       var xsiCurrPolygons = new ActiveXObject("XSI.Collection");
       xsiCurrPolygons.Add(plyPolygons(i));

       // Activate and apply the filter 
       var fltPolyIslandFilter = Application.Filters("Polygon_Island");
       var xsiCurrIslands = fltPolyIslandFilter.Subset(xsiCurrPolygons);

       // To return an actual PolygonFaceCollection instead of an
       // XSICollection, we can convert it via the SubComponent 
       var plyCurrIslands = Dictionary.GetObject(xsiCurrIslands).SubComponent.ComponentCollection;

       // Indicate that we've see all of these components (optimization) 
       for ( var j=0; j<plyCurrIslands.Count; j++ ) {
          arrSeen[plyCurrIslands(j).Index] = 1;
       }

       // Add the PolygonFaceCollection of polygon islands to the return array
       arrIslands.push(plyCurrIslands);
   }

   return arrIslands;
}
 
 
// Open the club bot sample scene and select the feet polygon mesh
var strClubBot = XSIUtils.BuildPath(
   Application.InstallationPath(siFactoryPath),
   "Data", "XSI_SAMPLES", "Scenes", "club_bot.scn"
);
OpenScene(strClubBot, false);
SelectObj("club_bot.BotFeet");

// Using this in a tool, you might use the selection:
var e = new Enumerator(Selection);
for ( ; !e.atEnd(); e.moveNext() ) {
   var obj = e.item();
   var arrPolyIslands = GetIslands(obj);
   Application.LogMessage( "# of polygon islands: " + arrPolyIslands.length );
}

// Expected results:
// INFO : # of arrPolyIslands: 2

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