[vtkusers] picking vtkImageSlice using vtkCellPicker?

[Miro Drahos]

Hi David,
thank you for your prompt response.

I am using VTK 5.10 and doing nothing special as far as I can tell. Here 
is some more details:

I have a vector of vtkSmartPointer<vtkImageSlice> objects to display 
images [my 3D CT image has several segments with different slice 
thicknesses, so that's why I have a vector of them]. All the reslicing 
and visualization is working as expected, so I don't suspect an issue 
there.
Now I am observing LeftMouseEvent of the interactor and processing it in 
my callback class to recognize when the surface model is picked. If it 
is, then user can translate and rotate it. The callback class is derived 
from both vtkCommand and QObject (to be able to use signal/slots of Qt 
that this is part of) and I am implementing FindPickedActor(int x, int 
y) method as I have seen it throughout VTK many times.
I have tried to use different pickers, and decided for vtkCellPicker 
instead of vtkPropPicker, to be able to set tolerance (user can make the 
surface model transparent and then might want to pick just the outline 
-- intersection of the surface and the image reslice plane. Picking 
outline is hard with no tolerance).
Picking surface model works just fine.

Here is the Print() of one of my vtkImageSlice instance:

vtkImageSlice (0x4ecbd30)
   Debug: Off
   Modified Time: 64690
   Reference Count: 3
   Registered Events: (none)
   Dragable: On
   Pickable: On
   AllocatedRenderTime: 860.822
   EstimatedRenderTime: 0
   NumberOfConsumers: 1
   RenderTimeMultiplier: 0.863803
   Visibility: On
   PropertyKeys: none.
   useBounds: 1
   IsIdentity: true
   Position: (0, 0, 0)
   Orientation: (0, 0, 0)
   Origin: (0, 0, 0)
   Scale: (1, 1, 1)
   Bounds:
     Xmin,Xmax: (-100, 100)
     Ymin,Ymax: (-100, 100)
     Zmin,Zmax: (-90.625, -2.5)
   UserTransform: (none)
   UserMatrix: (none)
   Property:
     Debug: Off
     Modified Time: 64690
     Reference Count: 3
     Registered Events: (none)
     ColorWindow: 260.1
     ColorLevel: 119.85
     UseLookupTableScalarRange: Off
     LookupTable: 0x156088a0
     Opacity: 1
     Ambient: 0.3
     Diffuse: 1
     InterpolationType: Linear
     LayerNumber: 0
     Checkerboard: Off
     CheckerboardSpacing: 10 10
     CheckerboardOffset: 0 0
     Backing: Off
     BackingColor: 0 0 0
   Mapper:
     Debug: Off
     Modified Time: 96181
     Reference Count: 3
     Registered Events: (none)
     Executive: 0x4ecc950
     ErrorCode: Success
     Information: 0x4ecc440
     AbortExecute: Off
     Progress: 1
     Progress Text: (None)
     TimeToDraw: 0
     ClippingPlanes: (none)
     SlicePlane: 0x4691280
     SliceAtFocalPoint: Off
     SliceFacesCamera: Off
     Border: On
     Background: Off
     NumberOfThreads: 8
     JumpToNearestSlice: Off
     AutoAdjustImageQuality: On
     SeparateWindowLevelOperation: On
     ResampleToScreenPixels: On
     SlabThickness: 0
     SlabType: Mean
     SlabSampleFactor: 2
     ImageSampleFactor: 1
     Interpolator: 0x4ecf330
   Bounds: (-100, 100) (-100) (100) (-90.625) (-2.5)

I will make a simple mock program and try to isolate the problem.
Thank you once again!
Miro



On 03/20/2014 12:31 PM, David Gobbi wrote:
> Hi Miro,
>
> You'll have to provide more details, because I use vtkCellPicker on
> vtkImageSlice all the time.  It's even part of the nightly VTK testing.
> Is there anything special about the way you use the vtkImageSlice?
> What version of VTK are you using?
>
>    David
>
> On Thu, Mar 20, 2014 at 1:15 PM, Miro Drahos <mdrahos at robodoc.com> wrote:
>> Hi all,
>> I am rendering an image slice using vtkImageSlice and a surface (vtkActor).
>> When I perform picking using vtkCellPicker, I always pick the surface actor,
>> even if it is in the background, behind the vtkImageSlice.
>> If I try to pick the vtkImageSlice (and the ray does not intersect the
>> surface actor), the Pick() method returns 0, as well as picker->GetPath()
>> returns NULL. The vtkImageSlice is set to be pickable.
>> I am quite baffled by this, since I'd expect to be able to pick
>> vtkImageSlice with vtkCellPicker, since it is a vtkProp3D.
>> If I use vtkPropPicker, I can pick the image slice fine, but I would prefer
>> to use vtkCellPicker so that I can specify picking tolerance.
>> Can someone shed some light on this?
>> Thank you tons!
>> Miro