public LSL_Rotation llRotBetween(LSL_Vector a, LSL_Vector b)
{
if (!ScriptProtection.CheckThreatLevel(ThreatLevel.None, "LSL", m_host, "LSL", m_itemID))
{
return(new LSL_Rotation());
}
//A and B should both be normalized
LSL_Rotation rotBetween;
// Check for zero vectors. If either is zero, return zero rotation. Otherwise,
// continue calculation.
if (a == new LSL_Vector(0.0f, 0.0f, 0.0f) || b == new LSL_Vector(0.0f, 0.0f, 0.0f))
{
rotBetween = new LSL_Rotation(0.0f, 0.0f, 0.0f, 1.0f);
}
else
{
a = LSL_Vector.Norm(a);
b = LSL_Vector.Norm(b);
double dotProduct = LSL_Vector.Dot(a, b);
// There are two degenerate cases possible. These are for vectors 180 or
// 0 degrees apart. These have to be detected and handled individually.
//
// Check for vectors 180 degrees apart.
// A dot product of -1 would mean the angle between vectors is 180 degrees.
if (dotProduct < -0.9999999f)
{
// First assume X axis is orthogonal to the vectors.
LSL_Vector orthoVector = new LSL_Vector(1.0f, 0.0f, 0.0f);
orthoVector = orthoVector - a * (a.x / LSL_Vector.Dot(a, a));
// Check for near zero vector. A very small non-zero number here will create
// a rotation in an undesired direction.
rotBetween = LSL_Vector.Mag(orthoVector) > 0.0001
? new LSL_Rotation(orthoVector.x, orthoVector.y, orthoVector.z, 0.0f)
: new LSL_Rotation(0.0f, 0.0f, 1.0f, 0.0f);
}
// Check for parallel vectors.
// A dot product of 1 would mean the angle between vectors is 0 degrees.
else if (dotProduct > 0.9999999f)
{
// Set zero rotation.
rotBetween = new LSL_Rotation(0.0f, 0.0f, 0.0f, 1.0f);
}
else
{
// All special checks have been performed so get the axis of rotation.
LSL_Vector crossProduct = LSL_Vector.Cross(a, b);
// Quarternion s value is the length of the unit vector + dot product.
double qs = 1.0 + dotProduct;
rotBetween = new LSL_Rotation(crossProduct.x, crossProduct.y, crossProduct.z, qs);
// Normalize the rotation.
double mag = LSL_Rotation.Mag(rotBetween);
// We shouldn't have to worry about a divide by zero here. The qs value will be
// non-zero because we already know if we're here, then the dotProduct is not -1 so
// qs will not be zero. Also, we've already handled the input vectors being zero so the
// crossProduct vector should also not be zero.
rotBetween.x = rotBetween.x / mag;
rotBetween.y = rotBetween.y / mag;
rotBetween.z = rotBetween.z / mag;
rotBetween.s = rotBetween.s / mag;
// Check for undefined values and set zero rotation if any found. This code might not actually be required
// any longer since zero vectors are checked for at the top.
if (double.IsNaN(rotBetween.x) || double.IsNaN(rotBetween.y) ||
double.IsNaN(rotBetween.z) || double.IsNaN(rotBetween.s))
{
rotBetween = new LSL_Rotation(0.0f, 0.0f, 0.0f, 1.0f);
}
}
}
return(rotBetween);
}
