[vtkusers] vtkTriangleStrip and empty vtkSTLWriter output

[Bill Lorensen]

I looked at the STLWriter code:

1) It reports an error if a polygon is not a triangle.
2) It reports nothing if there are triangle strips.

At a minimum I think it should handle triangle strips. No need to run
triangle filter, I'll decompose the strips on the fly.

Working on a patch and a unit test.

Bill

On Thu, Oct 15, 2015 at 9:45 AM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> I think the writer should handle triangle strips. I'll take a stab at adding
> that functionality.
>
> On Oct 15, 2015 9:13 AM, "Ben Boeckel" <ben.boeckel at kitware.com> wrote:
>>
>> On Wed, Oct 14, 2015 at 22:34:25 -0400, David Cole via vtkusers wrote:
>> > Shouldn't the STL writer detect that its input contains non-triangles,
>> > and
>> > **automatically** insert a triangle filter to produce correct output?
>> > Or,
>> > at the very least, spit out an error message saying "here, insert this
>> > code
>> > before calling Update/Write, and it will work like you want it to" ... ?
>>
>> Well, it used to drop vertices past the third on the floor (silently),
>> but now it should be erroring out about non-triangles at least:
>>
>>     commit 9a00db82900bd15442cc471143c4e5dd1ac09a2d
>>     Author: Ben Boeckel <ben.boeckel at kitware.com>
>>     Date:   Tue Feb 25 17:16:58 2014 -0500
>>
>>         STLWriter: Raise an error for non-triangles
>>
>>         The STL format only supports triangles and previously, it just
>>         truncated polygons silently. Cause an error to occur when this
>>         happens so that users know.
>>
>>         Change-Id: I9c2f96d887074943130a8442d6796cb0c2ce1bbf
>>
>> The commit is in VTK 6.2.0.
>>
>> > (Similarly for rendering crappy polydata using the polydata mapper: it
>> > requires up-to-date normals to render with proper lighting and shading,
>> > and
>> > seems like the perfect candidate for **automatically** inserting a
>> > polydata
>> > normals filter. This might be harder to detect that the normals are not
>> > up
>> > to date, but sure would have saved my team some time recently...)
>>
>> It should error out like the STL writer for bad input at the least.
>>
>> > Would these types of improvements be welcome additions to VTK, or am I
>> > missing some case where you would NOT want this type of behavior?
>>
>> As long as it lets you know that your data is bad and that (and how) it
>> is being fixed is warned about, I don't see any reason why such an
>> auto-fixer filter couldn't exist (whether it is named vtkSTLWriter or
>> something else is a different question I don't have enough feel too
>> strongly about).
>>
>> --Ben
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Please keep messages on-topic and check the VTK FAQ at:
>> http://www.vtk.org/Wiki/VTK_FAQ
>>
>> Search the list archives at: http://markmail.org/search/?q=vtkusers
>>
>> Follow this link to subscribe/unsubscribe:
>> http://public.kitware.com/mailman/listinfo/vtkusers



-- 
Unpaid intern in BillsBasement at noware dot com