Thanks Robert, I get closer to it.
Just for verification:
If I have i.e. 10 vertexes and I get 20 calls to the callback method each
defining a triangle.
Each call gives me 3 indexes, 3 normals and 3 texcoords.
Right now I just push everything into the corresponding arrays and at the end
I call:
geometry->addPrimitiveSet(new
osg::DrawArrays(osg::PrimitiveSet::TRIANGLES, 0, osgVertexIndices->size()));
You say this will not work because:
1) geometry->setNormalBinding(osg::Geometry::BIND_PER_PRIMITIVE_SET);
expects just 1 normal for the whole thing (?)
2) Texture coordinates are allways bound per vertex?
In this case I have to:
1) initialize a normal array with Vec3(0.0, 0.0, 0.0)
for each triangle callback I have to look on each vertex index , if the
indexes normal is 0
if yes: just set it
if no: duplicate the vertex at the end of the vertexes and push_back
the normal
2) do something comparable on the texcoords
Is that your recommendation?
Is there any way to bind normals to the vertex indexes?
Thanks in advance!
- Werner -
Am Donnerstag, 26. August 2010 12:06:34 schrieb Robert Osfield:
> Hi Werner,
>
>
> BIND_PER_PRIMITIVE_SET will mean that you'll have one of the
> associated attribute (i.e. colour, normal) per osg::PrimitiveSet
> attached the osg::Geometry, so if you have one osg::DrawElementsUShort
> used for the triangles then you'll need just one of the associated
> attribute for it.
>
> BIND_PER_PRIMITIVE will apply the attribute per primitive in you case
> per triangle.
>
> Tex coords in the OSG are always bound per vertex, there isn't a
> control to alter this.
>
> If you have a vertex array and indices for your triangles the natural
> thing to do would be to use a osg::DrawElementsUShort(GL_TRIANGLES)
> then use push_back(tri.p1) for each index on each triangle.
>
> I would suggest binding the normals per vertex, you'll have to do this
> for the tex coords as well. If a single vertex will have multiple tex
> coords or multiple normals associated with it due to differences in
> the triangles then you'll need to duplicate the vertices and remap the
> indices on the triangles to fit this.
>
> Robert.
>
> On Thu, Aug 26, 2010 at 10:38 AM, Werner Modenbach
>
> <[email protected]> wrote:
> > Thank you Paul for your response.
> >
> > Yes, you are right, the solution isn't perfect at all. But I'm
> > integrating some external code which is just giving me a vertex array
> > and a per triangle callback with vertex indexes and normal and texture
> > coords.
> >
> > And further more I need some screenshots very urgently for a customer
> > presentation.
> >
> > The performance improvement has to wait :-(
> >
> > So I try to analyse why it's not working. And I detected something I
> > don't understand.
> > In my opinion it should give the same result having:
> > 1) one normal per triangle an binding PER_PRIMITIVE
> > 2) 3 times the same normal and binding PER_PRIMITIVE_SET
> >
> > But it doesn't. So I'm confused.
> >
> > Thanks for further hints.
> >
> > - Werner -
> >
> > Am Mittwoch, 25. August 2010 22:41:14 schrieb Paul Martz:
> >> Werner Modenbach wrote:
> >> > Maybe someone can give me some explanation on my stupid little
> >> > problem.
> >> >
> >> > I have a geometry being composed of TRIANGLES.
> >> > I have a vertex-array, a verted-index-array and a normal-array
> >> > assigned to my geometry.
> >>
> >> Off-topic: Do you need to use the vertex-index-array? It is deprecated:
> >> /** deprecated - forces OpenGL slow path, just kept for
> >> backwards compatibility.*/
> >> void setVertexIndices(IndexArray* array);
> >>
> >> > 3 indexes and 3 normals per Triangle.
> >> > Normal binding is set to BIND_PER_PRIMITIVE_SET.
> >> >
> >> > Unfortunately the rendering shows the geometry flat in curious dark
> >> > colors and some unexpected light behaviour.
> >> > For analysis purpose I set the normal binding to BIND_PER_PRIMITIVE
> >> > and pushed just 1 normal per TRIANGLE.
> >> > Everything looks good except I see the triangles and the geometry
> >> > isn't smooth.
> >> > The next test is pushing the same normal vector 3 times and setting
> >> > the binding back to BIND_PER_PRIMITIVE_SET.
> >> > In my understanding this should give the same optical result as
> >> > before. Unfortunately it doesn't and everything is dark again.
> >> >
> >> > I guess, I misunderstand something with the normal bindings.
> >> >
> >> > Any hint is highly appreciated. Thanks in advance
> >>
> >> I'm not sure why you don't use BIND_PER_VERTEX, as you stated above that
> >> your normal array contains 3 normals per triangle, so you have one
> >> normal per vertex, right?
> >>
> >> BIND_PER_PRIMITIVE would result in flat shading (only one normal used
> >> for each triangle -- which, by the way, also forces OpenGL down the
> >> slow path), and BIND_PER_PRIMITIVE_SET would be even more granular: one
> >> normal used for each PrimitiveSet you add to the Geometry. This would
> >> make all triangles in the PrimitiveSet either uniformly dark or
> >> uniformly lit, depending on the direction of the one normal used for
> >> the whole group.
> >>
> >> For analysis purposes, I suggest using the normals pseudoloader:
> >> > osgviewer dumptruck.osg.normals
> >>
> >> Hope that helps,
> >> -Paul
> >>
> >> _______________________________________________
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> >> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.or
> >> g
> >
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> >
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> >
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