[vtkusers] Problems with vtkClipPolyData and vtkImplicitBoolean

[David Gobbi]

On Fri, Jan 8, 2016 at 5:55 AM, David Gobbi <david.gobbi at gmail.com> wrote:

>
> When a vtkPlaneCollection is used for clipping, the clipping is done once
> for each plane (so if there are six planes, then the data is clipped six
> times).  In general, you can always combine implicit functions in this way:
> clip the data with each function (keeping both the "inside" part and the
> "outside" part), and then use a boolean to combine the data pieces back
> together again.  By properly merging points when combining the pieces back
> together, it's possible to do this seamlessly even for "or" operations.
>

Hmm, I don't think I did a good job of describing this, so I'll try again,
using just two implicit functions to keep it simple:
1) clip the data with the 1st implicit function, keep both the inside and
outside parts.
2) clip each output with the 2nd implicit function, again keep the inside
and outside
3) at this point, there will be 4 data sets (some may be empty), and the
boolean operation can be used to decide which ones to keep and which to
throw away
4) the "kept" data sets can be appended to put them back together again
5) line segments that had been cut and then put back together can be
re-combined to make the result seamless

 - David
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