[vtkusers] Generic vtkMatrix

[Aashish Chaudhary]

I think it will be really useful to have it. Last week I was looking  
for something similar...

Also Passing array (pointers) is not the best thing without passing  
the size of the array which I think will be gone if we pass the  
vectors (or there references)

Regards


Sent from my mobile device


On Nov 25, 2009, at 9:10 AM, David Doria <daviddoria+vtk at gmail.com>  
wrote:

> On Tue, Nov 24, 2009 at 11:44 PM, Aashish Chaudhary <aashish.chaudhary at kitware.com 
> > wrote:
> Hi,
>
> I have extensively  used GMTL library. Similar to Eigen its headers  
> only and LGPL license
>
> http://ggt.sourceforge.net/
>
> It worked reasonably well with VTK and some other SceneGraph  
> libraries for some of the projects me and my colleagues worked on  
> earlier. May be some of concepts can be ported to VTK if not used  
> directly?
>
> ~Regards,
> Aashish
>
>
> On Tue, Nov 24, 2009 at 11:02 PM, Marcus D. Hanwell <marcus.hanwell at kitware.com 
> > wrote:
> On Tue, Nov 24, 2009 at 10:05 PM, David Doria <daviddoria+vtk at gmail.com 
> > wrote:
> I really think it would be nice to have something in VTK to allow  
> users to do simple matrix/vector multiplication/addition/transpose/ 
> etc without much effort and fighting ** type variables.  It will  
> also greatly improve the interface to many of the vtkMath functions.
>
> I have started working on vtkMatrix here:
> http://www.rpi.edu/~doriad/VTK_List/vtkMatrix/
>
> Take a look at Example.cxx to see the syntax. Can I get some initial  
> comments? Is it something that users actually want/actually has a  
> chance of making it to VTK? Is this the right structure/way to go  
> about writing such a thing? Is there any way we could include some  
> things from VNL in VTK as ITK does to avoid reinventing the wheel?
>
> What about using a general purpose library such as Eigen when more  
> features are needed?
>
> http://eigen.tuxfamily.org/
>
> It has a liberal license (LGPL with template instantiation  
> exceptions), is header only, provides a well developed and general  
> purpose C++ template library with a great syntax. You can also get  
> at the underlying pointers to the data, this could be assigned to  
> the vtkMatrix4x4 for example. I have used it in previous projects.
>
> I have not had much time to experiment with how easily it can be  
> mixed with VTK code, but it should be reasonably simple. It would of  
> course add an extra dependency to your project, and could not be  
> used in VTK code.
>
> Marcus
> -- 
> Marcus D. Hanwell, Ph.D.
> R&D Engineer, Kitware Inc.
> (518) 881-4937
> -- 
> Aashish Chaudhary
>
>
> These are good suggestions for general purpose things. However, I  
> was more interested in improving the interface to the vtkMath  
> functions, as well as providing developers in VTK source an easy way  
> to do these things. I realize vtkMatrix3x3 and vtkMatrix4x4 cover  
> many cases of matrix manipulations - but even doing something as  
> simple as subtracting/adding vectors the user has to write their own  
> little subtraction loop:
>
> double a[3];
> double b[3];
> //...fill a and b ...
> double c[3];
>
> // Should be easy as c = a-b
> //instead, we have to do:
> for(unsigned int i = 0; i < 3; i++)
> {
> c[i] = a[i] - b[i];
> }
>
> That just seems like something that is done quite often and is  
> representative of the kind of thing that should have a little more  
> "wrapping" (i.e. a vtkPoint or vtkVector class).
>
> Do you not agree that VTK needs some built-ins like this?
>
> Thanks,
>
> David
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