[vtkusers] Question on vtkImageData::ComputeStructuredCoordinates

[justfrom]

Hi All,

now i have a issue on vtkImageData::ComputeStructuredCoordinates,

the issue begin with i use vtkProbeFilter to plot a line on a volume data,
and one end of the line is out of the volume, such as

--
assume: volume dims is 30x30x30, spacing all 1.0, origion is (0,0,0), then
it's bound is [0.0, 29.0] and one point of the plotting line is x=29.2 in
world coordinates
--

but ComputeStructuredCoordinates calc point ( x=29.2 )'s ijk[0]=29, then the
align it to ijk[0] = 28 with pcoord[x]=1.0

so, sample points x=29.2, x=29.4, x=29.6, x=29.8 get equal value, the the
plotting line is odd where i think the value should drop to zero

if this is a interpolation out of bound, why when x= -0.1,
ComputeStructuredCoordinates align to -1 (use floor) to elimate the
interpolation?

could someone help me, or maybe it's my misunderstand some concepts? i
appreciate.

thanks and regards

just
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