public static bool PlanePlaneIntersection(out Vector3 linePoint, out Vector3 lineVec, Vector3 plane1Normal, Vector3 plane1Position, Vector3 plane2Normal, Vector3 plane2Position)
{
linePoint = Vector3.zero;
lineVec = Vector3.zero;
//We can get the direction of the line of intersection of the two planes by calculating the
//cross product of the normals of the two planes. Note that this is just a direction and the line
//is not fixed in space yet. We need a point for that to go with the line vector.
lineVec = Vector3.Cross(plane1Normal, plane2Normal);
//Next is to calculate a point on the line to fix it's position in space. This is done by finding a vector from
//the plane2 location, moving parallel to it's plane, and intersecting plane1. To prevent rounding
//errors, this vector also has to be perpendicular to lineDirection. To get this vector, calculate
//the cross product of the normal of plane2 and the lineDirection.
Vector3 ldir = Vector3.Cross(plane2Normal, lineVec);
float denominator = Vector3.Dot(plane1Normal, ldir);
//Prevent divide by zero and rounding errors by requiring about 5 degrees angle between the planes.
if(Mathf.Abs(denominator) > 0.006f){
Vector3 plane1ToPlane2 = plane1Position - plane2Position;
float t = Vector3.Dot(plane1Normal, plane1ToPlane2) / denominator;
linePoint = plane2Position + t * ldir;
return true;
}
//output not valid
else{
return false;
}
}
