[Rtk-users] Forward project a geometric phantom

[louie]

Dear rtk users,

I ran into a small problem with the geometric phantom filter (rtk::DrawGeometricPhantomImageFilter).

Here comes the description:

Input:
Geometry: Magnification = 1 (virtual detector at the image center)

GeometricFile: [Box]  A=50.         B=50.             C=50.          x=0.        y=0.           z=0.        beta=0        gray=5.
Spacing: 1
Dimension: 150
centered.

Projection stack: 
Spacing: 1
Dimension: 1500 (much larger than the projection)

Projector: 
CudaForwardProjectionImageFilter (step=0.1)

Problem:
If I connect the output of drawGeometricPhantom filter to the input of the projector (input 1), the result has non-zero pixels on the projection image which is not part of the projection.
If I write and read the output drawGeometricPhantom filter to and from the disc first, the result is correct, i.e. there is nothing but the projection of the object.

Question:
Can anyone reproduce this? Why is there such a difference? 

Best regards,
Louie
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