[vtkusers] ICP not working well

Wes Turner wes.turner at kitware.com
Mon Mar 23 09:13:12 EDT 2009

My apologies ... as always haste makes waste.  I edited what I wrote to make
it (slightly) more readable.

On Mon, Mar 23, 2009 at 9:05 AM, Wes Turner <wes.turner at kitware.com> wrote:

> David,
> I just took a quick look, so you probably need to do some analysis on your
> own to fully resolve this issue.  Looking at the data sets, it appears that
> you are sampling Bunny.vtp (source) and using it to sample points from
> BunnyScan.vtp (target) using ICP.  Since BunnyScan only contains the front
> side of Bunny, any points sampled from the rear surface of Bunny will not
> find a true match and will end up pulling BunnyScan away from the front
> surface and more toward the center of Bunny.  This is consistent with the
> data you are showing.
> You might be able to get what you are looking for simply by swapping the
> source and target in the ICP and using that as the transform to apply to
> BunnyScan, moving it towards Bunny.  If you need the inverse transform
> (moving Bunny towards BunnyScan) you will need to explicitly calculate the
> inverse transform by grabbing the Matrix4x4 from the ICP on completion,
> inverting it, and applying it as the transform to Bunny.  Directly inverting
> the icp will not work as it just swaps source and target which will get you
> right back to your current state.
> All of this is from memory, so your mileage may vary.
> - Wes
> On Sat, Mar 21, 2009 at 11:48 AM, David Doria <daviddoria at gmail.com>wrote:
>> Here are my input files / output file:
>> http://www.rpi.edu/~doriad/Bunny/ <http://www.rpi.edu/%7Edoriad/Bunny/>
>> I am trying to register Bunny.vtp to BunnyScan.vtp and the result is in
>> MatchedBunny.vtp
>> Here are my settings:
>>     vtkIterativeClosestPointTransform * icp =
>> vtkIterativeClosestPointTransform::New();
>>     icp->SetMaximumNumberOfIterations(1000);
>>     icp->SetMaximumMeanDistance(1e-6);
>>     icp->GetLandmarkTransform()->SetModeToRigidBody();
>> I believe I am calling everything correctly because the resulting point
>> cloud is much nearer than the original. However it seems to still be
>> significantly wrong. Anyone know why this would be?
>> Thanks,
>> David
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> --
> Wesley D. Turner, Ph.D.
> Kitware, Inc.
> R&D Engineer
> 28 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-371-3971 x120

Wesley D. Turner, Ph.D.
Kitware, Inc.
R&D Engineer
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-371-3971 x120
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