These are chat archives for highfidelity/hifi

6th
Jul 2014
AlericInglewood
@AlericInglewood
Jul 06 2014 12:45
'morning... hmm, nobody here since I left again :\
Which shows, lines 431 to 438:
template <typename T> GLM_FUNC_QUALIFIER detail::tquat<T> inverse ( detail::tquat<T> const & q ) { return gtc::quaternion::conjugate(q) / gtc::quaternion::dot(q, q); }
Why are they dividing by the dot product of q with itself? It makes no sense imho.
Well, maybe if q isn't normalized... but shouldn't it always be normalized?
I think that hifi better use just conjugate, instead of inverse. Saves CPU :P
AlericInglewood
@AlericInglewood
Jul 06 2014 13:08
Hm, ok - I see that glm deals with quaternions in general - not just rotations. So, in our case using inverse would be overkill indeed.
AlericInglewood
@AlericInglewood
Jul 06 2014 19:00
Hmm, just got a nasty insight :\
While both, an orientation and a rotation can be represented by a quaternion; there are only two quaternions that you can use to represent a rotation (over an angle that isn't zero degrees) but there are an infinite number of quaternions to represent any given orientation...
I had written some code to calculate an orientation from a vector (relative to UP) and wasted three hours trying to find out why the result wasn't matching the rotation that I had applied :P
Clément Brisset
@Atlante45
Jul 06 2014 23:59
Not sure I get what you’re saying here? an orientation is a rotation relative to the coordinate system of reference. In essence a rotation and an orientation are the same operation.