Re: [script][5.11] Get difference between 2 rotations

[Nicolas Langlois <nicolasl(at)buzzimage.com>]

Ouch!

Guess I should've spent the time needed not to get laughed at by my 
colleagues reading Brent's reply! :)

Nicolas Langlois
Senior/Lead Rigger/TD
Buzz Image



Brent McPherson wrote:
> Bernard,
>
> I'm afraid Nicholas' solution is wrong.
>
> To find a true delta rotation you must multiply quaternions as Martin
> suggested, not subtract them.
>
> However, it also looks to me like there is a small typo in Martin's
> solution and it should be:
>
>    startQuat.InvertInPlace()
>    ^^^^^^^^^
>    deltaQuat.Mul(endQuat,startQuat)
>
> Cheers!
> --
> Brent
>
> -----Original Message-----
> From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf
> Of Bernard Lebel
> Sent: Thursday, October 04, 2007 9:14 PM
> To: XSI(at)Softimage.COM
> Subject: Re: [script][5.11] Get difference between 2 rotations
>
> All right thanks everyone, I'll see what I can from there.
>
> Cheers!
> Bernard
>
>
>
>
> On 10/4/07, Nicolas Langlois <nicolasl(at)buzzimage.com> wrote:
>   
> > Bernard,
> >
> > Maybe something like this:
> >
> > # PYTHON CODE
> >
> > import win32com.client
> > from win32com.client import constants
> > from win32com.client import Dispatch
> > XSIMath    = Dispatch('XSI.Math')
> >
> > # Get the items Transforms
> > oItemATransform = oItemsA.Kinematics.Global.Transform
> > oItemBTransform = oItemsB.Kinematics.Global.Transform
> > oItemCTransform = oItemsA.Kinematics.Global.Transform
> > oRotA = XSIMath.CreateRotation()
> > oRotB = XSIMath.CreateRotation()
> > oRotC = XSIMath.CreateRotation()
> > oItemATransform.GetRotation(oRotA)
> > oItemATransform.GetRotation(oRotB)
> >
> >
> > #Create Quaternions.
> > oRotA.GetQuaternion(q1)
> > oRotB.Quaternion(q2)
> >
> > #q1 = q1 - q2
> > q1.SubInPlace(q2)
> > oRotC.SetFromQuaternion(q1)
> >
> > oItemCTransform.SetRotation(oRotC)
> > oItemsC.Kinematics.Global.Transform = oItemCTransform
> >
> >
> > # END PYTHON CODE
> >
> > Nicolas Langlois
> > Senior/Lead Rigger/TD
> > Buzz Image
> >
> >
> >
> > Bernard Lebel wrote:
> >     
> > > Hello,
> > >
> > > I'd need some guidance here. Say I have 3 objects. I want the third
> > > object to get the rotational difference between the first two.
> > >
> > > In a simplified example, the first object has rotx 25.0, the second
> > > has rotx 15.0, so I'd want the third object to get rotx of 10.0.
> > >
> > > I'm not sure at all where to go from there, using the XSI math
> > > objects. Do I have to perform a subtraction for every axis of the
> > > rotation?
> > >
> > >
> > > Thanks
> > > Bernard
> > > ---
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