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osgconv "noTriStripPolygons" give tri. fans only


 
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KariR
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Joined: 12 Sep 2017
Posts: 2

PostPosted: Tue Sep 12, 2017 1:50 pm    Post subject:
osgconv "noTriStripPolygons" give tri. fans only
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Hi,

Converting an obj file to ive with osgconv gives me unexpected results with the option noTriStripPolygons in the OSG-3.4.1 release. The osgviewer stats tell me that the created model has more than four times as many vertices than the original obj file and only triangle fan primitives. One drawarray for every three vertices. In the OSG-3.0.1 build the same options gave me long drawarrays of TRIANGLES.
The options I use: osgconv -O "noRotation noTriStripPolygons noTesselateLargePolygons" myfile.obj myfile.ive

I want triangle primitives only, why do I get all too many triangle fans?

Thank you!

Cheers,
Kari
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robertosfield
OSG Project Lead


Joined: 18 Mar 2009
Posts: 11154

PostPosted: Wed Sep 13, 2017 11:07 am    Post subject:
osgconv "noTriStripPolygons" give tri. fans only
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Hi Kari,


Without testing the data or similar first hand is not possible to give you a definitive answer to what is going on. 



Could you post a link to your data or other data that exhibits similar behaviour?


As a general comment, it sounds like the scene graph is not well balanced, it might be that the original .obj file is poorly conditioned and needs work to restructure it into a more optimal way for real-time rendering. 



At lot time has passed between 3.0.1 and 3.4.1 so to know what changes have taken place, some have certainly been made to the OBJ in that period.  Perhaps a change in default behaviour is the reason.




Robert.


On 12 September 2017 at 14:50, Kari Ringdal < (
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Quote:
Hi,

Converting an obj file to ive with osgconv gives me unexpected results with the option noTriStripPolygons in the OSG-3.4.1 release. The osgviewer stats tell me that the created model has more than four times as many vertices than the original obj file and only triangle fan primitives. One drawarray for every three vertices. In the OSG-3.0.1 build the same options gave me long drawarrays of TRIANGLES.
The options I use: osgconv -O "noRotation noTriStripPolygons noTesselateLargePolygons" myfile.obj myfile.ive

I want triangle primitives only, why do I get all too many triangle fans?

Thank you!

Cheers,
Kari

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KariR
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Joined: 12 Sep 2017
Posts: 2

PostPosted: Thu Sep 14, 2017 8:38 am    Post subject:
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Hi Robert,

Thank you for your answer!

I have the same problem when viewing a simple model in osgviewer. I've included screenshots of the stats with and without the noStripPolygons option. The vertex count is 3241 with no options and 18960 with the option.

I use this model:
graphics.stanford.edu/courses/cs148-10-summer/as3/code/as3/teapot.obj

My OSG-3.4.1 was built on Windows 7 x64 with Visual Studio 2010.


Kari
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