public static float preciseangle(float3 v1, float3 v2)
{
var v3 = v1.normalized();
var v4 = v2.normalized();
return(math.dot(v1, v2) < 0 ?
math.PI - 2 * ((-v3 - v4).length() / 2).asin() :
2 * ((v3 - v4).length() / 2).asin());
}