[ITK-users] Creating 3D dome using ITK

[Matt McCormick]

Hi,

Depending on the code, MY_RADIUS may need to be divided by two.

To avoid difficulties like this, it is better to work in physical
space versus index space. For more information on how physical space
works in ITK, see the itk::Image overview in the ITK Software Guide:

  https://itk.org/ITKSoftwareGuide/html/Book1/ITKSoftwareGuide-Book1ch4.html#x38-450004.1


There is a filter that can be used to anti-alias the mask.  Here is an example:

  https://itk.org/ITKExamples/src/Filtering/AntiAlias/SmoothBinaryImageBeforeSurfaceExtraction/Documentation.html


I hope this helps.

Matt

On Wed, May 10, 2017 at 6:19 AM, sidharta <sidharta.gupta93 at gmail.com> wrote:
> Dear all,
>
> I am trying to make a 3D dome (ie; Half Sphere) and then generating a binary
> image out of it. The aim is to use this binary image as a mask in
> maskFilter. I was able to generate a 2D circular mask, which was straight
> forward. I used this in a maskFilter and masked the 3D image using
> slicebysliceFilter.
>
> I can think of two ways to do it:
> 1. Make several masks of decreasing circle radius which ultimately would
> represent a dome.
> 2. Make a mask image and assign the values at indices accordingly to get a
> dome mask.
>
> The first step seems doable but to my understanding would be an overkill.
> I am not able to do the second step. Following is the code I tried:
>
> float MY_RADIUS = maskRegion.GetSize()[0];
> MaskIteratorType iterator(maskImage, maskImage->GetLargestPossibleRegion());
> while (!iterator.IsAtEnd())
>         {
>                 const InputImageType::IndexType & index = iterator.GetIndex();
>                 std::cout << "Index is " << index;
>                 float value = (index[0] - centerPoint[0]) * (index[0] - centerPoint[0])
>                         + (index[1] - centerPoint[1]) * (index[1] - centerPoint[1]);
>                 std::cout << "Compare - LHS = " << value << " RHS = " << MY_RADIUS *
> MY_RADIUS << std::endl;
>                 if ((index[0] - centerPoint[0]) * (index[0] - centerPoint[0])
>                         + (index[1] - centerPoint[1]) * (index[1] - centerPoint[1])
>                         <= MY_RADIUS * MY_RADIUS)
>                 {
>                         iterator.Set(1);
>                 }
>                 --MY_RADIUS;
>                 ++iterator;
>         }
>
> After adding the cout commands I saw that --MY_RADIUS is incorrect. I
> generated the required sphere using matlab, just to get the values I should
> assign to the pixels.
>
> Additionally, I noticed there is a need for anti-aliasing to the mask.
> Kindly let me know how this can be done iteratively.
>
> Thank you!
>
>
>
> --
> View this message in context: http://itk-users.7.n7.nabble.com/Creating-3D-dome-using-ITK-tp38201.html
> Sent from the ITK - Users mailing list archive at Nabble.com.
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