[vtkusers] trying to clip a polyData with an other
David.Pont at ForestResearch.co.nz
David.Pont at ForestResearch.co.nz
Mon Mar 15 14:45:48 EST 2004
Hi Laurent,
just another thought, if you want to clip with an ovoid of specific size
you could use vtkSphere, SetTransform where vtkTransform->Scale is
something other than (x,x,x), eg: (2,1,1) to get an ovoid with known
dimensions. vtkSuperquadric is more general but do you really need that
much flexibility in shape?
In either case rendering a polygonized implicit surface (with opacity<1 or
as wireframe) will give visual feedback of size.
Dave P
Laurent Mundeleer
<lmundele at ulb.ac. To: David.Pont at ForestResearch.co.nz
be> cc: vtk <vtkusers at vtk.org>
Sent by: Subject: Re: [vtkusers] trying to clip a polyData with an
vtkusers-admin at vt other
k.org
12/03/2004 21:17
Hi David,
Eureka, I've two holes in my sphere! :)
Thanks for the tip. But it will be hardy to generate something with a
specified size...
Now I'd like to have a real sphere, not just a surface, but something
full on the inside, that will be cut by an ovoide. That will be simplier
to visualize.
I don't know if it's possible with vtkPolyData but maybe with a volume
(i'm not used to them), and using the clipVolume.
Thanks again for your help,
Laurent
David.Pont at ForestResearch.co.nz wrote:
>Hi Laurent,
> OK I got it:
>With your settings for the positions and sizes of the sphere and
>superquadric I could see from the colours on the sphere (scalars from
>GenerateClipScalarsOn) that the superquadric was 'close' to the left and
>right sides of the sphere (from SetScale(2,1,1)).
>
>There is a warning in the doc on vtkSuperquadric:
>"Warning:
>The Size and Thickness parameters control coefficients of superquadric
>generation, and may do not exactly describe the size of the superquadric."
>
>So I simply altered SetScale to 4,1,1 and got holes clipped on each side
of
>the sphere :-))
>Because you can not see an implicit surface, it is hard to know when your
>polydata and implicit surface are in contact.
>I have inserted my code below, note at the bottom I have used a class
>vtkImplicitPolygonizer to visualise the implicit surface. This is a class
I
>have implemented that creates polydata from an implicit surface, very
>useful.... As you obviously work in C++ I have attached the source code,
it
>may be useful for you... and I should contribute it to vtk as it seems to
>work OK and have a real use.....
>
> Happy clipping
> Dave P
>
>PS: thanks for the tip about responding to vtkusers and admin. I have
>noticed this in the past and have not figured out how this happens. Mail
>from the list is usually sent to or cc'd to just vtkusers. But when I
reply
>somehow vtkadmin gets added. We are forced to use a particular mail
program
>(which I hate with a passion), maybe it is finding vtkadmin in my address
>book and adding it ???? I will look closer at this....
>
>
>
> // polygonal sphere
> vtkSphereSource *pd1 = vtkSphereSource::New();
> pd1->SetThetaResolution( 16 );
> pd1->SetPhiResolution ( 16 );
> pd1->SetCenter( 0, 5, 0 );
> pd1->SetRadius( 10.0 );
>
> vtkSuperquadric *sq1 = vtkSuperquadric::New();
> sq1->SetCenter(0,5,0);
> sq1->SetSize(5);
>// sq1->SetScale(2,1,1);
> sq1->SetScale(4,1,1);
> sq1->ToroidalOff();
>
> vtkClipPolyData *clipper = vtkClipPolyData::New();
> clipper->SetInput( pd1->GetOutput() );
> clipper->SetClipFunction( sq1 );
> clipper->GenerateClipScalarsOn();
>
> vtkPolyDataMapper *Mapper = vtkPolyDataMapper::New();
> Mapper->SetInput( clipper->GetOutput() );
> vtkActor *Actor = vtkActor::New();
> Actor->SetMapper( Mapper );
> Renderer->AddActor( Actor );
>
> // polygonise the superquadric
>-------------------------------------------------------------------------
> float bounds[6] = { -20, 20, -10, 10, -10, 10 };
> vtkImplicitPolygonizer *ip1 = vtkImplicitPolygonizer::New();
> ip1->SetImplicitFunction( sq1 );
> ip1->SetBounds( bounds );
> ip1->SetNormalAngle( 30 ); // use lower angle to
>refine the surface more, default is 50
> ip1->SetMaximumAdaptations( 4 ); // use higher value to refine the
>surface more, default is 3
> vtkPolyDataMapper *Mapper2 = vtkPolyDataMapper::New();
> Mapper2->SetInput( ip1->GetOutput() );
> vtkActor *Actor2 = vtkActor::New();
> Actor2->SetMapper( Mapper2 );
> Actor2->GetProperty()->SetRepresentationToWireframe();
> Renderer->AddActor( Actor2 );
>
>
>(See attached file: vtkImplicitPolygonizer.h)(See attached file:
>vtkImplicitPolygonizer.cpp)
>
>
>
>
> Laurent Mundeleer
> <lmundele at ulb.ac. To:
David.Pont at ForestResearch.co.nz
> be> cc:
> Subject: Re: [vtkusers]
trying to clip a polyData with an
> 11/03/2004 22:53 other
>
>
>
>
>
>
>Hi David,
>see my interlaced comments ;-)
>
>David.Pont at ForestResearch.co.nz wrote:
>
>
>
>>Hi Laurent,
>> your sphere is at 0,0,0 radius 10, the superquadric is at 0,5,0 size 5.
>>This means they do not really intersect. Try sphere radius 5, or
>>superquadric size 10 for example. The superquadric should then clip a
hole
>>
>>
>>from the side of the sphere.
>
>
>>
>>
>I've juste tried (the superquadric had scale (2,1,1) so before it should
>cut the poly too) but no changes, also with a better resolution on the
>sphere :( >
>>Note that you can use SetInsideOut or SetGenerateClippedOutput +
>>GetClippedOutput to get the clipped piece also.
>>
>>
>>
>>
>now I try to visualize this, but it's still empty
>
>
>
>>The implicit function is only evaluated at the sphere points. If the
>>implicit surface only passes through the interior of a polygon no hole
>>
>>
>will
>
>
>>result. Increase Set*Resolution to get more points and thus more accurate
>>clipping. To remedy problems with accuracy in clipping general polydata
>>
>>
>you
>
>
>>can pass the polydata through vtkLinearSubdivisionFilter (2 or 3
>>iterations) before clipping. This simply makes smaller polygons and more
>>points, giving the clipper more accuracy.
>>
>>
>>
>>
>>
>I've tried this filter, no more changes...
>My clippedOutput is still empty but with a non-null length (???).
>
>
>
>>(NB: vtkSuperQuadric is actually vtkSuperquadric)
>>
>>
>>
>>
>bad typing ;-)
>
>
>
>>I am responding OFF the list to avoid being accussed of sending SPAM to a
>>Mr Byron Hale, until I figure out what is going on there ! ...
>>
>>
>>
>>
>I think you forward to vtkusers at vtk.org AND to vtkusers-admin at vtk.org,
>maybe you should remove the second one?
>
>
>
>> regards
>> Dave P
>>
>>
>>
>>
>thanks again
>Regards,
>Laurent
>
>
>
>>
>>
>>
>
>
>
>> Laurent Mundeleer
>>
>>
>
>
>
>> <lmundele at ulb.ac. To:
>>
>>
>David.Pont at ForestResearch.co.nz
>
>
>> be> cc:
>>
>>
>
>
>
>> Subject: Re: [vtkusers]
>>
>>
>trying to clip a polyData with an
>
>
>> 11/03/2004 03:55 other
>>
>>
>
>
>
>
>
>
>
>
>
>>
>>
>>Hi David,
>>
>>me again. I do just the same with a vtkSuperquadric, but now it seems
>>that nothing is clipped.
>>
>>---
>>vtkSuperQuadric *s = vtkSuperQuadric::New();
>>s->SetCenter(0,5,0);
>>s->SetSize(5);
>>s->SetScale(2,1,1);
>>s->ToroidalOff();
>>
>>vtkClipPolyData *clipper = vtkClipPolyData::New();
>>clipper->SetInput(tumorSample->GetInput()); // tumorSample has on input
>>a vtkSphereSource (center: 0,0,0 ; Radius : 10)
>>
>>clipper->SetClipFunction(s);
>>clipper->GenerateClipScalarsOn();
>>clipper->Update();
>>
>>tumorSample->SetInput(clipper->GetOutput());
>>aff->ChargerModel3D(tumorSample);
>>
>>---
>>
>>thanks again
>>
>>Laurent
>>
>>David.Pont at ForestResearch.co.nz wrote:
>>
>>
>>
>>
>>
>>>Hi Laurent,
>>> There is no way in vtk to clip one polydata with another.
>>>vtkClipPolyData evaluates an implicit function at each point position in
>>>the polydata and then clips each cell according to the implicit function
>>>value at its points. So you can only clip with implicit surfaces.
>>>
>>>
>>>
>>>
>>(Actually
>>
>>
>>
>>
>>>you can also clip using scalar values associated with the polydata.) So
>>>clipping and cutting in vtk is only done with implicit surfaces. Check
>>>
>>>
>the
>
>
>>>class doc for vtkImplicitFunction and see its descendants for the list
of
>>>possible 'shapes' you can clip with.
>>>GetOutput and SetThetaResolution belong to vtkSuperquadricSource which
>>>produces a polygonal surface, good to look at, but no use for clipping.
>>>vtkSuperquadric is an implicit surface, difficult to look at, but just
>>>right for clipping.
>>>
>>>hope that clarifies...
>>> Dave P
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>> Laurent Mundeleer
>>>
>>>
>>>
>>>
>>
>>
>>
>>> <lmundele at ulb.ac. To:
>>>
>>>
>>>
>>>
>>David.Pont at ForestResearch.co.nz
>>
>>
>>
>>
>>> be> cc: vtk
>>>
>>>
>>>
>>>
>><vtkusers at vtk.org>
>>
>>
>>
>>
>>> Sent by: Subject: Re: [vtkusers]
>>>
>>>
>>>
>>>
>>trying to clip a polyData with an
>>
>>
>>
>>
>>> vtkusers-admin at vt other
>>>
>>>
>>>
>>>
>>
>>
>>
>>> k.org
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>> 09/03/2004 22:11
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>>Hi David,
>>>
>>>thanks for your answer, the problem with vtkSuperquadric is that there's
>>>no GetOutput(), SetThetaResolution(),...
>>>
>>>Is there another way to do that?
>>>
>>>Thanks
>>>
>>>Laurent
>>>
>>>David.Pont at ForestResearch.co.nz wrote:
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>>Laurent,
>>>>vtkImplicitDataSet uses the data set scalars to perform clipping, I am
>>>>not sure what scalars (if any) are produced by vtkSuperqadricSource.
But
>>>>
>>>>
>>>>
>>>>
>>I
>>
>>
>>
>>
>>>>see there is vtkSuperquadric which can be passed directly to
>>>>vtkClipPolydata->SetClipFunction.
>>>>
>>>>Dave P
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>> Laurent Mundeleer
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>> <lmundele at ulb.ac. To: vtk
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>><vtkusers at vtk.org>
>>>
>>>
>>>
>>>
>>>
>>>
>>>> be> cc:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>> Sent by: Subject: [vtkusers] trying
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>to clip a polyData with an other
>>>
>>>
>>>
>>>
>>>
>>>
>>>> vtkusers-admin at vt
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>> k.org
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>> 08/03/2004 22:56
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>>Hi All,
>>>>
>>>>I'dl like to clip a vtkPolyData with another one.
>>>>Here's my code, based on the examples:
>>>>
>>>>---------------------
>>>>
>>>>vtkImplicitDataSet *v = vtkImplicitDataSet::New();
>>>>v->SetDataSet(ovoideSample->GetInput()); // ovoideSample has on input a
>>>>vtkSuperquadricSource
>>>>
>>>>vtkClipPolyData *clipper = vtkClipPolyData::New();
>>>>clipper->SetInput(tumorSample->GetInput()); // tumorSample has on input
>>>>a vtkSphereSource
>>>>
>>>>clipper->SetClipFunction(v);
>>>>clipper->GenerateClipScalarsOn();
>>>>clipper->Update();
>>>>
>>>>tumorSample->SetInput(clipper->GetOutput());
>>>>aff->ChargerModel3D(tumorSample);
>>>>
>>>>---------------------
>>>>
>>>>but after that my tumorSample is empty.
>>>>What do i wrong?
>>>>
>>>>Thanks in advance,
>>>>Regards
>>>>
>>>>Laurent
>>>>
>>>>
>>>>_______________________________________________
>>>>This is the private VTK discussion list.
>>>>Please keep messages on-topic. Check the FAQ at: <
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>>>>
--
********************************************
Laurent Mundeleer
Université Libre de Bruxelles (ULB)
Service des Systèmes Logiques et Numériques (SLN) CP165/57
50, Av. F.Roosevelt
1050 Bruxelles
Belgium
tel : ++32.2.650.22.97
fax : ++32.2.650.22.98
e-mail : lmundele at ulb.ac.be
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