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

[David Gobbi]

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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>> >
>> >
>> >
>> > --
>> > William J. Schroeder, PhD
>> > Kitware, Inc.
>> > 28 Corporate Drive
>> > Clifton Park, NY 12065
>> > will.schroeder at kitware.com
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>> > (518) 881-4902
>> >