[vtk-developers] Re: Adding vtkAbstractTransform::Shear() method

[Will Schroeder]

Makes sense, that was the path I was originally on. I thought that 
someone else might want to make use of this method at some point. Thanks,
Will

David Gobbi wrote:
> Hi Will,
>
> I didn't add shear originally because it could be performed by the appropriate combination of rotation and scale operations.
>
> Shear can be tough because (as with rotation) there are many ways to parameterize it.  It isn't possible to write a Shear method that will make everyone happy.
>
> I'd like to see it left out, personally, because Rotation, Scale, and Translation already form an orthogonal set that can be used to compose any linear transformation.  For an Affine widget (and this is just my opinion) it might be easiest to have code in the widget itself to build a vtkMatrix4x4.
>
>  - David
>
>
> ----- Original Message ----
> From: Will Schroeder <will.schroeder at kitware.com>
> To: David Gobbi <david_gobbi at rogers.com>
> Cc: vtk-developers at vtk.org
> Sent: Tuesday, October 17, 2006 8:40:41 AM
> Subject: Adding vtkAbstractTransform::Shear() method
>
> David-
>
> I am working on a VTK widget:: vtkAffineWidget and its representation 
> vtkAffineRepresentation2D. I would like to support shears which as you 
> know are affine transformations. To do this I've thought about adding a 
> vtkAbstractTransform::Shear() method to do the actual fiddling with the 
> transformation matrix, patterning it after the basic linear 
> transformations Translate, Scale and Rotate (i.e., using the internal 
> vtkTransformConcatenation). Are you okay with this? Other suggestions?
>
> Will
>
>
>
>
>