//Help method to calculate the intersection point between two planes offset in normal direction by a width
private static MyVector2 GetIntersectionPoint(MyVector2 a, MyVector2 b, MyVector2 c, float halfWidth, bool isTopPoint)
{
//Direction of the lines going to and from point b
MyVector2 beforeDir = MyVector2.Normalize(b - a);
MyVector2 afterDir = MyVector2.Normalize(c - b);
MyVector2 beforeNormal = GetNormal(a, b);
MyVector2 afterNormal = GetNormal(b, c);
//Compare the normals!
//normalDirFactor is used to determine if we want to top point (same direction as normal)
float normalDirFactor = isTopPoint ? 1f : -1f;
//If they are the same it means we have a straight line and thus we cant do plane-plane intersection
//if (beforeNormal.Equals(afterNormal))
//When comparing the normals, we cant use the regular small value because then
//the line width goes to infinity when doing plane-plane intersection
float dot = MyVector2.Dot(beforeNormal, afterNormal);
//Dot is 1 if the point in the same dir and -1 if the point in the opposite dir
float one = 1f - 0.01f;
if (dot > one || dot < -one)
{
MyVector2 averageNormal = MyVector2.Normalize((afterNormal + beforeNormal) * 0.5f);
MyVector2 intersectionPoint = b + averageNormal * halfWidth * normalDirFactor;
return(intersectionPoint);
}
else
{
//Now we can calculate where the plane starts
MyVector2 beforePlanePos = b + beforeNormal * halfWidth * normalDirFactor;
MyVector2 afterPlanePos = b + afterNormal * halfWidth * normalDirFactor;
Plane2 planeBefore = new Plane2(beforePlanePos, beforeNormal);
Plane2 planeAfter = new Plane2(afterPlanePos, afterNormal);
//Calculate the intersection point
//We know they are intersecting, so we don't need to test that
MyVector2 intersectionPoint = _Intersections.GetPlanePlaneIntersectionPoint(planeBefore, planeAfter);
return(intersectionPoint);
}
}
