"Trevor G Quayle" <Tin### [at] hotmailcom> schreef in bericht 
news:web.469e7741dedc19f1c150d4c10@news.povray.org...
> PdG <pdg### [at] INTERMERDAgmailcom> wrote:

>> For example: consider a cylinder. I've made it in blender, i've smoothed,
>> and render it. It goes well.
>> Now, every exports i made, the results is like this:
>>
>
> I've had a look at this and deconstructed the mesh.
> First of all, the normals all point inward, which isn't such a big deal, 
> as
> they all point inward, not just some.
>
> What is causing your problem though is the normals for the sides are not
> normal to the cylinder, they are oriented as if there is a smooth
> transition from the sides to the cap instead of being a sharp edge.  This
> causes POV to treat the mesh as being curved more like a sphere and shades
> it as such.  I don't use Blender, so I don't know how exporting works, but
> you need to limit the angle at which the normals are smoothed for, so the
> side meshes are smoothed around the cylinder, but not up and down the
> cylinder.
>

I translated PdG's cylinder (through Poseray) to Silo and come to the same 
conclusion concerning the normals' orientation inward. That should be easy 
to correct.

However, I think that the important keyword that PdG has used in his initial 
message is: "i've smoothed".
Smoothing (or subdividing) is the culprit here. What you can do in Silo for 
instance, is to "crease" the edges of the cylinder so that the shape remains 
the same. Otherwise, the cylinder will turn into a spherical object the more 
you smooth or subdivide. I suppose now that something like edge creasing 
should be done in Blender before exporting to POV-Ray.

Thomas

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