[vtkusers] units in VTK

[David Gobbi]

On Sat, Oct 25, 2014 at 4:11 PM, Sam Raby <rabysam28 at gmail.com> wrote:

> Hi,
>
> Consider an instant of vtkTubeFilter which has a method named "SetRadius".
> I was wondering how this Radius is related to millimeter?
>
> I am using vtkTubeFilter as an example but in general I wanted to know how
> units are involved in actors.
>

The VTK filters have no units.  It's the same as looking at the
equation y = m*x + b and asking what the units are:  all you can
tell for certain is that 'y' and 'b' have the same units, and that 'm'
has units of 'y/x'.  Other than that, it's up to whoever is using the
equation to decide on the units.  VTK is the same.

If you want to use millimeters, then set the radius in millimeters.
Just make sure that you use millimeters everywhere else, too.

Also make sure that all the files you load use millimeters.  If they
don't, you'll have to convert their units before you use them in your
pipeline.

 - David
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