/// <summary>
/// Returns the angle between 0 and 2*pi between the two vectors given.
/// </summary>
/// <param name="v1"></param>
/// <param name="v2"></param>
/// <returns></returns>
public static Radian Angle(VectorF2D v1, VectorF2D v2)
{
double size_v1 = v1.Size;
double size_v2 = v2.Size;
double dot = VectorF2D.Dot(v1, v2);
double cross = VectorF2D.Cross(v1, v2);
// filter out the vectors that are parallel.
if (v1[0] == v2[0] &&
v1[1] == v2[1])
{
return(0);
}
else if (v1[0] == v2[0] &&
v1[1] == -v2[1])
{
return(System.Math.PI / 2.0f);
}
else if (v1[0] == -v2[0] &&
v1[1] == v2[1])
{
return(-System.Math.PI / 2.0f);
}
else if (v1[0] == -v2[0] &&
v1[1] == -v2[1])
{
return(System.Math.PI);
}
// split per quadrant.
double angle;
if (dot > 0)
{ // dot > 0
if (cross > 0)
{ // dot > 0 and cross > 0
// Quadrant 1
angle = (double)System.Math.Asin(cross / (size_v1 * size_v2));
if (angle < System.Math.PI / 4f)
{ // use cosine.
angle = (double)System.Math.Acos(dot / (size_v1 * size_v2));
}
// angle is ok here for quadrant 1.
}
else
{ // dot > 0 and cross <= 0
// Quadrant 4
angle = (double)(System.Math.PI * 2.0f) + (double)System.Math.Asin(cross / (size_v1 * size_v2));
if (angle > (double)(System.Math.PI * 2.0f) - System.Math.PI / 4f)
{ // use cosine.
angle = (double)(System.Math.PI * 2.0f) - (double)System.Math.Acos(dot / (size_v1 * size_v2));
}
// angle is ok here for quadrant 1.
}
}
else
{ // dot <= 0
if (cross > 0)
{ // dot > 0 and cross > 0
// Quadrant 2
angle = (double)System.Math.PI - (double)System.Math.Asin(cross / (size_v1 * size_v2));
if (angle > System.Math.PI / 2f + System.Math.PI / 4f)
{ // use cosine.
angle = (double)System.Math.Acos(dot / (size_v1 * size_v2));
}
// angle is ok here for quadrant 2.
}
else
{ // dot > 0 and cross <= 0
// Quadrant 3
angle = -(-(double)System.Math.PI + (double)System.Math.Asin(cross / (size_v1 * size_v2)));
if (angle < System.Math.PI + System.Math.PI / 4f)
{ // use cosine.
angle = (double)(System.Math.PI * 2.0f) - (double)System.Math.Acos(dot / (size_v1 * size_v2));
}
// angle is ok here for quadrant 3.
}
}
return(angle);
}
public static Radian Angle(VectorF2D v1, VectorF2D v2)
{
double size1 = v1.Size;
double size2 = v2.Size;
double num1 = VectorF2D.Dot(v1, v2);
double num2 = VectorF2D.Cross(v1, v2);
if (v1[0] == v2[0] && v1[1] == v2[1])
{
return((Radian)0.0);
}
if (v1[0] == v2[0] && v1[1] == -v2[1])
{
return((Radian)(System.Math.PI / 2.0));
}
if (v1[0] == -v2[0] && v1[1] == v2[1])
{
return((Radian)(-1.0 * System.Math.PI / 2.0));
}
if (v1[0] == -v2[0] && v1[1] == -v2[1])
{
return((Radian)System.Math.PI);
}
double num3;
if (num1 > 0.0)
{
if (num2 > 0.0)
{
num3 = System.Math.Asin(num2 / (size1 * size2));
if (num3 < System.Math.PI / 4.0)
{
num3 = System.Math.Acos(num1 / (size1 * size2));
}
}
else
{
num3 = 2.0 * System.Math.PI + System.Math.Asin(num2 / (size1 * size2));
if (num3 > 7.0 * System.Math.PI / 4.0)
{
num3 = 2.0 * System.Math.PI - System.Math.Acos(num1 / (size1 * size2));
}
}
}
else if (num2 > 0.0)
{
num3 = System.Math.PI - System.Math.Asin(num2 / (size1 * size2));
if (num3 > 3.0 * System.Math.PI / 4.0)
{
num3 = System.Math.Acos(num1 / (size1 * size2));
}
}
else
{
num3 = -(System.Math.Asin(num2 / (size1 * size2)) - System.Math.PI);
if (num3 < 5.0 * System.Math.PI / 4.0)
{
num3 = 2.0 * System.Math.PI - System.Math.Acos(num1 / (size1 * size2));
}
}
return((Radian)num3);
}