>

Hi,

> Rene Weller wrote:
>> Hello,
>>> Could you please give a bit more details on what results you get  
>>> and how you obtain your triangle count?
>> your code works fine and reports the correct number of 7962  
>> triangles. But the stats-Function in the osgSceneViewer reports  
>> 7990 triangles for the same object.
>
> ok, thanks, now I can reproduce it. The difference in numbers comes  
> from the triangle striper that seems to introduce degenerate  
> triangles (although the stitch parameter is false). The Triangle  
> iterator skips these degenerate triangles, but since  
> calcPrimitiveCount (which is used by the statistics code) only  
> examines the length and type geo properties it counts them.
> Actually both numbers are correct in a sense, because  
> calcPrimitiveCount gives you the number of triangles that are sent  
> to the graphics card while the TriangleIterator only gives you  
> "real" triangles.
>
> @Johannes: Can you comment on this behavior of the striper, please?  
> Is it expected to generate additional triangles even when stitch is  
> false?

Yes, this behavior is correct. It creates degenerated triangles to  
swap the order of the last two vertices.

Normally the algo tries to extend the strip to build a sequence of  
left-right turns. If only one adjacent
face is available, we have to introduce a swap (i.e. a left-left or  
right-right turn), and therefore have to
insert a degenerated triangle.

regards,
johannes

>
>       Thanks,
>               Carsten

---
Dr.-Ing. Johannes Behr  tel: +49-6151-155-510
Fraunhoferstr. 5                        fax: +49-6151-155-196
D-64283 Darmstadt               skype: johannesbehr
Germany                         web: www.igd.fhg.de/www/igd-a4/



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