[osg-users] Quaternion Multiply

Matt Sutton Matt.Sutton at padtinc.com
Fri Sep 12 14:27:36 PDT 2008


Hi Folks,

   I know I must be missing something, but can someone help me out with
this.  It is true that multiplying two quaternions, a and b, can be seen
as a linear transform of one on the other, right?  So, for quaternions
a, b and c you can have something like:

 

c = a*b

 

Option 1: Using a linear transform on b constructed from a

c = A*b

Option 2: Using a linear transform on a constructed from b  

c = B*a

 

Note that matrices A and B have a slightly different construction since
the product of two quaternions is not commutative.

 

But, it looks to me like the OSG implementation is effectively using
option 1, but constructing the "A" matrix from the b quaternion? So, it
looks like a*b is actually b*a.  Is that intended?   If I'm totally
seeing this wrong, please forgive me.  I've attached a test file.

 

Thanks,

Matt Sutton

www.padtinc.com

 

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