/*
* Returns a Quaternion representing the angle between two vectors
*/
kmQuaternion* kmQuaternionBetweenVec3(kmQuaternion* pOut, const kmVec3* u, const kmVec3* v) {
kmVec3 w;
kmScalar len;
kmQuaternion q;
if(kmVec3AreEqual(u, v)) {
kmQuaternionIdentity(pOut);
return pOut;
}
len = sqrtf(kmVec3LengthSq(u) * kmVec3LengthSq(v));
kmVec3Cross(&w, u, v);
kmQuaternionFill(&q, w.x, w.y, w.z, kmVec3Dot(u, v) + len);
return kmQuaternionNormalize(pOut, &q);
}
kmQuaternion* kmQuaternionExtractRotationAroundAxis(const kmQuaternion* pIn, const kmVec3* axis, kmQuaternion* pOut) {
/**
Given a quaternion, and an axis. This extracts the rotation around the axis into pOut as another quaternion.
Uses the swing-twist decomposition.
http://stackoverflow.com/questions/3684269/component-of-a-quaternion-rotation-around-an-axis/22401169?noredirect=1#comment34098058_22401169
*/
kmVec3 ra;
kmScalar d;
kmVec3Fill(&ra, pIn->x, pIn->y, pIn->z);
d = kmVec3Dot(&ra, axis);
kmQuaternionFill(pOut, axis->x * d, axis->y * d, axis->z * d, pIn->w);
kmQuaternionNormalize(pOut, pOut);
return pOut;
}
/**< Normalizes a quaternion*/
kmQuaternion* kmQuaternionNormalize(kmQuaternion* pOut,
const kmQuaternion* pIn)
{
kmScalar length = kmQuaternionLength(pIn);
if (fabs(length) < kmEpsilon)
{
pOut->x = 0.0;
pOut->y = 0.0;
pOut->z = 0.0;
pOut->w = 0.0;
return pOut;
}
kmQuaternionFill(pOut,
pOut->x / length,
pOut->y / length,
pOut->z / length,
pOut->w / length
);
return pOut;
}
ParticlePrototype::ParticlePrototype() : Drawable()
{
kmVec3Fill(&scale, 0.2,0.2,0.2);
kmQuaternionFill(&rotation, 1.0, 0.0, 0.0, 0.0);
}
