Question

I need to convert this function to v3 API. This function is used to create an ellipse under a marker when selected. I have tried with projection and overlay, but without success.

  function makePolyPoints(_marker)
  {
    var polyPoints = Array();
    var markerPoint=  _marker.getLatLng();
    var projection = G_NORMAL_MAP.getProjection();
    var mapZoom = map.getZoom();
    var clickedPixel = projection.fromLatLngToPixel(markerPoint, mapZoom);
    var  ellipseRadA = 20;
    var ellipseRadB = 10;

    var polyNumSides = 20;
    var polySideLength = 18;

    for (var a = 0; a<(polyNumSides+1); a++) {
        var aRad = polySideLength*a*(Math.PI/180);
        var pixelX =  clickedPixel.x + ellipseRadA * Math.cos(aRad);
        var pixelY = -3 + clickedPixel.y + ellipseRadB * Math.sin(aRad);
        var polyPixel = new GPoint(pixelX,pixelY);
        var polyPoint = projection.fromPixelToLatLng(polyPixel,mapZoom);
        polyPoints.push(polyPoint);
    }
    return polyPoints;
}

Here the function for v3 that doesn’t work, i think a problem of zoom level but I can’t find how to replace projection.fromLatLngToPixel(markerPoint, mapZoom);

function makePolyPoints(_marker)
{
    var polyPoints = Array();
    var markerPoint=  _marker.getPosition();
    var projection = map.getProjection();
    var mapZoom = map.getZoom();
    var clickedPixel = projection.fromLatLngToPoint(markerPoint);

    var  ellipseRadA = 20;
    var ellipseRadB = 10;

    var polyNumSides = 20;
    var polySideLength = 18;

    for (var a = 0; a<(polyNumSides+1); a++) {
        var aRad = polySideLength*a*(Math.PI/180);
        var pixelX =  clickedPixel.x + ellipseRadA * Math.cos(aRad);
        var pixelY = -3 + clickedPixel.y + ellipseRadB * Math.sin(aRad);
        var polyPixel = new google.maps.Point(pixelX,pixelY);
        var polyPoint = projection.fromPointToLatLng(polyPixel);
        polyPoints.push(polyPoint);
    }
    return polyPoints;
}

Answer 1

Hmm.. Im going to use one of my favorite gmap examples to help you out.

Using var clickedPixel = projection.fromLatLngToPoint(markerPoint); dont give you yet clickedPixel coordinates, they are still world coordinates. See projection specs.

Specifying own mercator projection when calculating that kind of stuff is useful. Look closely to following lines: (in this code example)

var worldCoordinate = projection.fromLatLngToPoint(chicago);
    var pixelCoordinate = new google.maps.Point(
    worldCoordinate.x * numTiles,
    worldCoordinate.y * numTiles);

(you can view source with firebug or similar).

If you dont have it (in mozilla: Tools -> web developer -> page source)

Hopefully, this will help you get through the problem 🙂