Region

Unity Engine
1

Are there any built in functions to determine if a point in space is inside a region if you can provide the point in 2d (x,y) and the polygon as a series of coordinates in 2d as well. The coordinates do not need to refer to actual coordinates but just as an abstract function. I can provide the values for the coordinates. Something like PointInPoly.

Thanks for the help.

2

There’s Rect.Contains() but that’s only for rectangles.

–Eric

3

Thanks that might actually work for what I’m doing. If anybody knows of a way to do it with polygons let me know. Thanks.

4

I did a bit of Googling, found a code snippet in C and translated it, so here we are:

static function PolyContainsPoint (polyPoints : Vector2[], point : Vector2) : boolean {
	var j = polyPoints.Length-1;
	var inside = false;
	for (i = 0; i < polyPoints.Length; j = i++) {
		if ( ((polyPoints[i].y <= point.y  point.y < polyPoints[j].y) || (polyPoints[j].y <= point.y  point.y < polyPoints[i].y)) 
			(point.x < (polyPoints[j].x - polyPoints[i].x) * (point.y - polyPoints[i].y) / (polyPoints[j].y - polyPoints[i].y) + polyPoints[i].x))
			inside = !inside;
	}
	return inside;
}

So obviously you’d use it something like

var polygonArray : Vector2[];	// Array of points making up polygon
var point : Vector2;

function Start () {
	if (PolyContainsPoint(polygonArray, point)) {
		print ("Inside! Yay!");
	}
	else {
		print ("Outside! Brr, cold out here!");
	}
}

–Eric

5

Wow thanks so much for doing that. I hope you can find a use for it as well. Thanks so much!!