[Paraview] SWKey: How to Clean-up an STL datum set?

[Samuel Key]

Greetings Utkarsh!

Your advice is exceptional; the remaining "unwanted" STL triangles 
attached to the desired STL surface have been removed.

A couple of lessons:

(1) At first the instruction sequence seemed to me a little awkward. 
However, after repeated use it became rhythmic. I did find it better to 
reset/uncheck *Invert Selection* of the*Edit | Find Data* panel before 
going to the next location.

(2) It took a couple of tries for me to discover that the unwanted 
fin-like attachments were actually zero-thickness regions with matching 
back-to-back STL-triangles -- one for each side, and hence, it required 
a second removal go around. (The original 30+ layered tetrahedral mesh 
as our Japanese colleagues would say, "was not so good.")

(3) A triangular hole required a hand-crafted STL-triangle with a 
borrowed normal-vector from a neighbor triangle. After writing out the 
datum set, hand editing the STL-file to add in the missing triangle and 
renaming a copy of the datum-set, a read and write with PV showed that 
PV 'corrected' the normal vector. Whoever wrote that section of code 
deserves a pat on the back.

(4) The PV window with the row of miniature icons in upper-left corner 
took me a couple of  tries to figure out that add & subtract were clues 
to use ctrl & shift keys when making selections. IMHO, well done.

(5) Message to myself: "The more you use ParaView, the smarter it gets."

Thanks for really great tool!

Sam Key
On 3/21/2017 6:45 AM, Utkarsh Ayachit wrote:
> You can use the *Extract Selection* filter. Before you create the 
> filter, make sure you invert the selection so that you are removing 
> the selected selected. To do that, once you've made your selection, go 
> to *Edit | Find Data* and then check the *Invert Selection *check box. 
> Now, from the dialog itself, you can click the *Extract 
> Selection* button to create a new *Extract Selection* filter. The 
> output of this filter is *Unstructured Grid * and STL only supports 
> *Polydata, *hence apply the *Extract Surface* filter again and then 
> you shall be able to save out the result as a new STL file.
>
> Hope that helps.
> Utkarsh
>
> On Mon, Mar 20, 2017 at 5:18 PM, Samuel Key <samuelkey at bresnan.net 
> <mailto:samuelkey at bresnan.net>> wrote:
>
>     Hello All,
>
>     I am working with a less than perfect STL surface. I was able to
>     use PV's Clip filter spheres to remove a number of spatially
>     isolated undesirable triangle clusters.  (With a new application
>     of the Extract Surface Filter, I was able to use Save Data to get
>     an updated/revised STL file.)
>
>     I am now working on removing triangles that have a point or an
>     edge attached like a fish fin to the desired STL surface. I have
>     successfully selected the undesirable fin-like triangles. Now, I
>     want to delete (or Clip) these triangles to remove  them from the
>     datum set. Right-click delete does not appear to be an option?
>
>     Is there some way to delete these selected STL triangles from the
>     Datum set?
>
>     Regards,
>
>     Sam Key
>     FMA Development
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