# Check When a Point is Inside a Mesh

## How To Check When Point is Inside a Mesh

This mesh method takes a Vector3 point and checks if it inside the mesh.

## Design Outline

1. Check if point inside or outside of bounding box, when inside continue with following checks;
2. Cast a ray from the point in the positive and negative x directions;
3. When there is a hit, move forward from hit point a very small amount along ray direction and recast ray from new point;
4. Count hits, when zero or an odd number of hits then point is inside mesh and for a even number of hits > 0 non zero then point is outside of mesh.

## Design Method

1. Check bounding box;
var boundInfo = this.getBoundingInfo();var max = boundInfo.maximum;var min = boundInfo.minimum;if(point.x < min.x || point.x > max.x) {	return false;}if(point.y < min.y || point.y > max.y) {	return false;}if(point.z < min.z || point.z > max.z) {	return false;}
1. Use the diameter of the mesh's bounding sphere as the distance to cast the ray
var diameter = 2 * boundInfo.boundingSphere.radius;ray = new BABYLON.Ray(point, direction, diameter);
1. Set hit count to zero, while hits occurring increment hit count
var hitCount = 0;var pickInfo = ray.intersectsMesh(this);while (pickInfo.hit) {		hitCount++;	pickInfo.pickedPoint.addToRef(direction.scale(0.00000001), point); //move point a small amout in ray direction	ray.origin  = point;	pickInfo = ray.intersectsMesh(this);}
1. Count hits.
if((hitCount % 2) === 1) {	var pointFound = true;}else if ((hitCount % 2) === 0 && hitCount > 0) {	var pointFound = true;}
return pointFound;

## The Whole Function

Returns true if point is inside mesh, false otherwise.

BABYLON.Mesh.prototype.pointIsInside = function (point) {    	var boundInfo = this.getBoundingInfo();	var max = boundInfo.maximum;	var min = boundInfo.minimum;	var diameter = 2 * boundInfo.boundingSphere.radius;	if(point.x < min.x || point.x > max.x) {		return false;	}	if(point.y < min.y || point.y > max.y) {		return false;	}	if(point.z < min.z || point.z > max.z) {		return false;	}
var pointFound = false;	var d = 0;	var hitCount = 0;	var gap = 0;	var distance = 0;	var ray = new BABYLON.Ray(BABYLON.Vector3.Zero(), BABYLON.Axis.X, diameter);;	var pickInfo;	var direction = point.clone();    var refPoint = point.clone();
hitCount = 0;	ray.origin = refPoint;    ray.direction = direction;    ray.distance = diameter;			pickInfo = ray.intersectsMesh(this);	while (pickInfo.hit) {			hitCount++;		pickInfo.pickedPoint.addToRef(direction.scale(0.00000001), refPoint);		ray.origin  = refPoint;		pickInfo = ray.intersectsMesh(this);	}		if((hitCount % 2) === 1) {		pointFound = true;	}		return pointFound;};

## Playground Example

Generate random points in a volume around a twelve pointed star mesh. Place a sphere at each point and turn it red when inside the star.

Twelve Pointed Star