[vtkusers] picking vtkImageSlice using vtkCellPicker?

[David Gobbi]

Hi Miro,

I checked through the git logs, the only recent fix to vtkCellPicker
had to do with the fact that GetMapper() returned null for
vtkImageSlice (but it still returned the prop and position just fine).
 However, I noticed that the only nightly test for picking images uses
a vtkImageActor (a subclass of vtkImageSlice) instead of using
vtkImageSlice directly.  This shouldn't make a difference, but it
might be worth investigating.

  David

On Thu, Mar 20, 2014 at 2:17 PM, Miro Drahos <mdrahos at robodoc.com> wrote:
> 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
>
>