[vtk-developers] A new way to look at images

Mon Jan 24 16:46:07 EST 2011

David,

It would be great to have mapper that respected dicom's image
orientation and the difference between vtk's graphics oriented image
coordinate system and itk's image(medical)-oriented coordinate system.
These are huge sources of confusion in the graphics versus imaging
communities.

Keep up the good work,

Bill

On Mon, Jan 24, 2011 at 4:38 PM, David Gobbi <david.gobbi at gmail.com> wrote:
> Hi Will,
>
> I'll see if I can get everything onto the wiki this week.  I haven't
> figured out all the names yet, the reslicing mapper is the only one
> that I've written so far.
>
> One thing that I should add is that, when it is all done, I plan to
> make vtkImageActor into a subclass of the new vtkImage class.
> At that point, vtkImageActor will become a special vtkImage that
> has a built-in mapper and a built-in SetInput() method (purely for
> backwards compatibility).
>
> Replacing vtkImageActor has been on my agenda for years now.
> It doesn't "fit" the VTK pipeline properly:
> - it has no VTK5-style SetInputConnection method (and cannot,
>  since it isn't a vtkAlgorithm)
> - since it has no mapper or property, it can't work with vtkLODProp3D
> - it requires "unsigned char" input: it would be nice if it could do
>  the color mapping and window/level itself
>
> These are all things that my new design will address (and of course I
> also needed a new mapper that could do reslicing).  The overall goal
> is to improve the way that images are displayed and interacted with,
> by putting image display on an equal footing with volume and geometry
> display.
>
> Ah... I said that I'd put the info on the wiki, so I guess I don't need to
> put everything in this email.  Thanks for your support thus far.
>
>  - David
>
>
> On Mon, Jan 24, 2011 at 1:53 PM, Will Schroeder
> <will.schroeder at kitware.com> wrote:
>> Hi David-
>> I see what you are saying and it makes sense, I am wondering what would
>> be the names of the various image mappers  (since you indicate that there is
>> more than one)?
>> W
>>
>> On Sat, Jan 22, 2011 at 10:33 AM, David Gobbi <david.gobbi at gmail.com> wrote:
>>>
>>> Hi Will,
>>>
>>> I did think of ImageSliceActor and several other names, but the issue
>>> is the "reslicing" is done by the mapper class, not by the actor
>>> class.  So right now I have my vtkImage class paired with a mapper
>>> that displays images by reslicing them.  By I also intend to write
>>> another mapper for viewing 2D images.
>>>
>>> The idea here is that the three major Prop3D types will be vtkActor,
>>> vtkVolume and vtkImage.
>>>
>>> The vtkImage class would be the definitive image-viewing class for
>>> VTK.  It would have:
>>> 1) a mapper that reslices the image and displays the slice
>>> 2) a mapper that does what vtkImageActor does
>>> 3) a mapper for doing slice display of vtkUnstructuredGrid data
>>> 4) down the line, perhaps some GPU-specialized mappers
>>>
>>> What I'm trying to say here is that the reslicing behaviour that I
>>> described in my previous email is all in the mapper.  The vtkImage
>>> "actor" class, on the other hand, is meant to be very generic.  It is
>>> just a Prop3D that image-related mappers can be attached to.
>>>
>>>  David
>>>
>>>
>>> On Sat, Jan 22, 2011 at 7:32 AM, Will Schroeder
>>> <will.schroeder at kitware.com> wrote:
>>> > David this is very clever and seems pretty intuitive to use (I did not
>>> > actually try it).
>>> > I think my initial (minor) concern is naming, while I think what you've
>>> > come
>>> > up is pretty good I can see how a novice might get confused.  Did you
>>> > consider something like "ImageResliceActor", "ResliceActor" or simply
>>> > "Reslice"?
>>> > W
>>> >
>>> >
>>> > On Fri, Jan 21, 2011 at 6:53 PM, David Gobbi <david.gobbi at gmail.com>
>>> > wrote:
>>> >>
>>> >> Hi All,
>>> >>
>>> >> I've been experimenting with a new way of rendering 3D images in VTK.
>>> >> So far, it is working fairly well.  Here is a rough description of the
>>> >> new VTK classes I've written:
>>> >>
>>> >> vtkImage - a new prop for image viewing, analogous to vtkVolume and
>>> >> vtkActor
>>> >> vtkImageProperty - holds the lookup table, window/level, etc.
>>> >> vtkImageMapper3D - a new mapper that does image reslicing and texturing
>>> >>
>>> >> Using these classes is very simple: just set up the camera, and the
>>> >> vtkImage object will automatically display the slice at the camera
>>> >> focal point.  To show a different slice, just move the focal point so
>>> >> that it lies at a different position in the 3D image.  To slice in a
>>> >> different orientation, rotate the camera around the focal point.  In
>>> >> other words, the slicing is completely controlled by the camera.  This
>>> >> makes everything work nicely with the VTK interactors, and also
>>> >> simplifies the intermixing of images and geometry.
>>> >>
>>> >> My reason for making this class is that I've seen plenty of users on
>>> >> the list who struggle with vtkImageReslice and with vtkImageViewer.  I
>>> >> wanted to make it as easy to view an image in VTK as it is to view an
>>> >> actor. I have the code on my github account
>>> >> git://github.com/dgobbi/VTK.git in the branch "image-prop"
>>> >> http://github.com/dgobbi/VTK/tree/image-prop
>>> >>
>>> >> The code includes a modified vtkInteractorStyleImage class that has
>>> >> new interactions for rotating the camera with shift-leftbutton (for
>>> >> oblique slicing) and for adjusting the focal point with
>>> >> shift-middlebutton (for slicing through the image).  There is also a
>>> >> python example in Examples/ImageProcessing/Python/ImageMapper3D.py.
>>> >> All of this is still preliminary development, but so far I haven't
>>> >> encountered any show-stopping bugs.
>>> >>
>>> >> Please let me know what you think.  I'll try to make a wiki page with
>>> >> more details next week.
>>> >>
>>> >>  - David
>>> >> _______________________________________________
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>>> >>
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>>> >>
>>> >
>>> >
>>> >
>>> > --
>>> > William J. Schroeder, PhD
>>> > Kitware, Inc.
>>> > 28 Corporate Drive
>>> > Clifton Park, NY 12065
>>> > will.schroeder at kitware.com
>>> > http://www.kitware.com
>>> > (518) 881-4902
>>> >
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