void Update()
{
if (polygon == null)
{
return; // Only having polygon
}
// Layout winding direction object if any.
bool hasWindingDirectionObject = (windingDirectionObject != null);
bool windingChanged = (polygon.windingDirection != _previousWindingDirection);
if (hasWindingDirectionObject && windingChanged)
{
windingDirectionObject.transform.localScale = (polygon.isCW) ? Vector3.one : new Vector3(1.0f, -1.0f, 1.0f);
windingDirectionObject.transform.rotation = (polygon.isCW) ? Quaternion.identity : Quaternion.Euler(new Vector3(0.0f, 0.0f, 90.0f));
}
// Layout area text mesh if any.
bool hasAreaTextMesh = (areaTextMesh != null);
bool areaChanged = (polygon.area != _previousArea);
if (hasAreaTextMesh && areaChanged)
{
areaTextMesh.text = polygon.area.ToString();
}
// Track.
_previousWindingDirection = polygon.windingDirection;
_previousArea = polygon.area;
}
public static Vector2 CentroidOfPolygons(Polygon[] polygons, Polygon.WindingDirection windingDirection = Polygon.WindingDirection.Unknown)
{
if (windingDirection == Polygon.WindingDirection.Unknown)
{
windingDirection = polygons[0].windingDirection;
}
// From https://en.wikipedia.org/wiki/Centroid#By_geometric_decomposition
float ΣxA = 0.0f;
float ΣyA = 0.0f;
float ΣA = 0.0f;
foreach (Polygon eachPolygon in polygons)
{
// Add or subtract area.
float sign = (eachPolygon.windingDirection == windingDirection) ? 1.0f : -1.0f;
float eachSignedArea = eachPolygon.area * sign;
// Get centroid.
Vector2 eachCentroid = eachPolygon.centroid;
// Sum weighted.
ΣxA += eachCentroid.x * eachSignedArea;
ΣyA += eachCentroid.y * eachSignedArea;
ΣA += eachSignedArea;
}
// "Remove" area.
float x = ΣxA / ΣA;
float y = ΣyA / ΣA;
return(new Vector2(x, y));
}