[vtkusers] Relationship between MinZBound and Position for a vtkVolume

[Elvis Stansvik]

2016-09-16 14:23 GMT+02:00 David Gobbi <david.gobbi at gmail.com>:
> I might have time for a longer answer later, but for now, I suggest you look
> at vtkImageChangeInformation.

Thanks David, and no hurry/expectations. I'll have a look at that.

Elvis

>
>  - David
>
> On Fri, Sep 16, 2016 at 6:19 AM, Elvis Stansvik
> <elvis.stansvik at orexplore.com> wrote:
>>
>> 2016-09-16 14:15 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>> > 2016-09-16 13:26 GMT+02:00 Elvis Stansvik
>> > <elvis.stansvik at orexplore.com>:
>> >> This is a very basic question, but I feel like I've missed something
>> >> fundamental.
>> >>
>> >> I have a volume which I set the position for using SetPosition. I'm
>> >> not applying any other transformations such as rotation or scale.
>> >>
>> >> What surprises me is that after having set the position, if I look at
>> >> the MinZBound of the volume, it doesn't correspond to the Z position I
>> >> set.
>> >>
>> >> E.g. if I (after I set the position of the volume) do
>> >>
>> >>     qDebug() << "MinZBound:" << volume->GetMinZBound();
>> >>     qDebug() << "Position[3]" << volume->GetPosition()[2];
>> >>
>> >> I can get output such as:
>> >>
>> >>     MinZBound: -0.162738
>> >>     Position[3] -0.165138
>> >>
>> >> I thought that the bounds of a volume was in VTK world coordinates. If
>> >> so, shouldn't MinZBound be exactly the Z position?
>> >>
>> >> Thanks for any clarifications, I've probably missed something simple.
>> >
>> > I forgot to say that in the X and Y axes, there seems to always be a
>> > correspondance after my SetPosition(..):
>> >
>> > MinXBound: -0.0299
>> > Position[0] -0.0299
>> > MinYBound: -0.0299
>> > Position[1] -0.0299
>> >
>> > I can't see what's special about the Z direction. What else affects
>> > the bounds of the vtkVolume? The reason I'm asking, and what made me
>> > discover this, is that my volumes don't show up at the positions I
>> > expect them to.
>> >
>> > I'm sure I've missed something trivial, but I'm at a loss as to what it
>> > is :/
>>
>> A perhaps important piece of information is that the vtkVolume uses a
>> vtkImageData that was the result of a vtkExtractVOI (taking a piece of
>> the image in the Z direction). So.. is there something special I
>> should watch out for regarding the bounds of the resulting image when
>> using vtkExtractVOI?
>>
>> I found this old and unanswered post from 2006 where someone else was
>> seeing strange bounds after a vtkExtractVOI:
>>
>>     http://www.vtk.org/pipermail/vtkusers/2006-December/039113.html
>>
>> Or perhaps that poster also suffers from the same confusions I am at the
>> moment?
>>
>> Elvis
>>
>> >
>> > Elvis
>> >
>> >>
>> >> Elvis
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>
>