[vtkusers] Re : closest point on a surface / vtkIterativeClosestPointTransform

[Steffen Oeltze]

Hi Jason,

sorry for the delay. With "surface" I refer to the original surface 
(vtkPolyData) NOT to the masked points.

Steffen

Jason Taclas schrieb:
> I have been trying to follow your suggestions, but I am somewhat hung up 
> on the data set;
> When you say
>        locator->SetDataSet(data); // data represents the surface
> what is the representation of the surface?  Is it the surface itself, or 
> the maskpoints vertices data?  I had originally imagined using the 
> vertices to represent the surface in the locator, and measure the 
> distance to this surface representation from a different point cloud, 
> but your description takes the vertices, distorts them with noise and 
> displaces the noisy vertices representation in space.  I have been 
> having trouble using locators (my application tends to crash at the 
> implimentation of the "findclosestpoint" method), and I wonder if it is 
> because I am using the wrong data set, be it from the filter producing 
> my surface, or the maskpoints vertices data.
> 
> Jason
> 
> On Thu, Feb 21, 2008 at 4:57 AM, Steffen Oeltze 
> <stoeltze at isg.cs.uni-magdeburg.de 
> <mailto:stoeltze at isg.cs.uni-magdeburg.de>> wrote:
> 
>     Yes, it works. Instead of creating the surface, I import a surface.
>     Then, I'm using vtkMaskPoints as well to randomly select surface
>     vertices. Next, I apply some noise to these vertices, a little bit of
>     translation and rotation. Finally, I use the ICP to bring the points
>     back to the surface.
> 
>     Then, I measured the Euclidean distance between the transformed points
>     (before and after ICP) and the surface. For that purpose, I use:
> 
> 
>     vtkCellLocator *locator = vtkCellLocator::New();
>            locator->SetDataSet(data); // data represents the surface
>            locator->SetNumberOfCellsPerBucket(1);
>            locator->BuildLocator();
>            locator->Update();
> 
>     in a loop:
> 
>     locator->FindClosestPoint(inPoint, closestPointOnSurface, cell_id,
>     sub_id, dist2);
> 
>     Cheers,
>     Steffen
> 
> 
> 
> 
>     Jason Taclas schrieb:
>      > have you gotten this to work?  I'm having trouble on a similar
>     project;
>      > I am also using vtkIterativeClosestPoint to register a point
>     cloud to a
>      > surface, and I also need to make distance measurements.  If it
>     matters
>      > at all, my surface was created with vtkMarchingCubes.  I used
>      > vtkMaskPoints with GenerateVerticesOn to get to vertices, is this
>     what
>      > you did?
>      >
>      > On Feb 15, 2008 9:21 AM, Steffen Oeltze
>      > <stoeltze at isg.cs.uni-magdeburg.de
>     <mailto:stoeltze at isg.cs.uni-magdeburg.de>
>      > <mailto:stoeltze at isg.cs.uni-magdeburg.de
>     <mailto:stoeltze at isg.cs.uni-magdeburg.de>>> wrote:
>      >
>      >     Thanks a lot for the hint! I'm using vtkCellLocator now to
>     determine the
>      >     closest point on a surface for a given position in 3D.
>      >
>      >     Steffen
>      >
>      >     cedric.schwartz at enst-bretagne.fr
>     <mailto:cedric.schwartz at enst-bretagne.fr>
>      >     <mailto:cedric.schwartz at enst-bretagne.fr
>     <mailto:cedric.schwartz at enst-bretagne.fr>> schrieb:
>      >      > Hi,
>      >      > As far as I know you can't have the distance information
>     with the ICP
>      >      > transform. Maybe you should try vtkPointLocator or
>     vtkKdTree in
>      >     order to
>      >      > obtain the distance measure.
>      >      > Cedric
>      >      >
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