/// <summary>
/// builds the Polygon edge normals. These are lazily created and updated only by the edgeNormals getter
/// </summary>
void buildEdgeNormals()
{
// for boxes we only require 2 edges since the other 2 are parallel
var totalEdges = isBox ? 2 : points.Length;
if (_edgeNormals == null || _edgeNormals.Length != totalEdges)
{
_edgeNormals = new Vector2[totalEdges];
}
Vector2 p2;
for (var i = 0; i < totalEdges; i++)
{
var p1 = points[i];
if (i + 1 >= points.Length)
{
p2 = points[0];
}
else
{
p2 = points[i + 1];
}
var perp = Vector2Ext.perpendicular(ref p1, ref p2);
Vector2Ext.normalize(ref perp);
_edgeNormals[i] = perp;
}
return;
}
void preparePolygonForCollisionChecks()
{
// we need to setup a Polygon with one edge. It needs the center to be in the opposite direction of it's normal.
// this is necessary so that SAT knows which way to calculate the MTV, which uses Shape positions.
var perp = Vector2Ext.perpendicular(_particleTwo.position - _particleOne.position);
perp.Normalize();
// set our Polygon points
var midPoint = Vector2.Lerp(_particleOne.position, _particleTwo.position, 0.5f);
_polygon.position = midPoint + perp * 50;
_polygon.points[0] = _particleOne.position - _polygon.position;
_polygon.points[1] = _particleTwo.position - _polygon.position;
_polygon.recalculateCenterAndEdgeNormals();
}