[osg-users] VRML Normal Issue

Ben Axelrod baxelrod at coroware.com
Tue Mar 24 09:06:24 PDT 2009


Thanks for the info.  Is this standard procedure with mesh files?  Because I have noticed similar affects with a variety of file formats.

I agree that when no normals are specified, the proper behavior for the parser is to use one normal per face, and calculate the face normals from the vertex points, but the shading I see in badbox.wrl does not look like one normal per face, it looks like one normal per vertex.  The shading of goodbox.wrl looks like one normal per face to me.  Am I mistaken on how these should look?

Thanks,
-Ben


-----Original Message-----
From: osg-users-bounces at lists.openscenegraph.org [mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Jan Ciger
Sent: Saturday, March 21, 2009 12:23 PM
To: OpenSceneGraph Users
Subject: Re: [osg-users] VRML Normal Issue

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Hello Ben,

Ben Axelrod wrote:
> I have noticed a very strange issue regarding VRML file rendering.  This
> issue happens in OSG viewer version 2.6, with openVRML version 0.14.3.
>
...
> Are there some VRML flags to prevent this behavior?  Is this a bug in
> the VRML parser?  If so, is this part of OSG or openVRML?

I happen to be one of the authors of the VRML plugin. I had a look at
your files and badbox.wrl is incorrect. You need to explicitly specify
the vertex normals, otherwise it will assume normal per face and if even
those are not provided, calculate them from the vertices - leading to
the behavior you are describing. The behavior is correct, IMO - the
parser has no means to know what you want if you do not specify the normals.

Regards,

Jan
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