static vector3 slerp(vector3 start, vector3 end, T percent) {
T dot = start.dot(end);
dot = vector3::clamp(dot, -1.0f, 1.0f);
T theta = acos(dot) * percent;
vector3 relative = end - start*dot;
relative.normalize();
return ((start * cos(theta)) + (relative*sin(theta)));
}
double get_rotation_angle(vector3<float> u, vector3<float> v) {
u.normalize();
v.normalize();
double cosine_theta = u.dot(v);
// domain of arccosine is [-1, 1]
if (cosine_theta > 1) {
cosine_theta = 1;
}
if (cosine_theta < -1) {
cosine_theta = -1;
}
double angle = acos(cosine_theta);
return angle;
}
