[vtkusers] what kind of scale do the world coordinates use?

[Fabrice Vincent]

1) The measurement unit is defined by the data you read. If your data contains point coordinates in
mm
then all measurements will be in mm
  if you read a volume of pixels and use  the SetDataSpacing of the vtkImageReader, you also
implicitly define a unit

2) May be the projection used by the camera doesn't preserve the distances. Try to use a parallele
projection ( vtkCamera  SetParalleleProjection).

Fabrice

Tao-Pak Chris Tsui wrote:

> Dear All VTK users
>
> I am using the annotatePick.tcl example given by the
> book to give me the coordinates of my CT skull
> slices...
>
> here are the questions:
>
> 1) are the coordinates readings I got in mm or it's
> just an arbitrary measurement units determinted by
> VTK??

>
> 2) I got several points marked on the skull and the
> distances between 2 points seem not to be proportional
> when I compare what I got from the computer screen
> with the actual skull I have..   is there any way to
> solve this?  or can I simply change the reading to mm?
>
> Thanks a lot
>
> Chris
>
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--
Fabrice VINCENT

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