[Bf-python] Collada Importer - Issue with Mesh Vertex Normals

[Khalifa Lame]

Thanks very much for the info and quick response. Though it answers my
question for the most part, it has created a few more questions for me.
Like how then does one find those references to the shared normals? Are
they interleaved with the poly indices. I'm not using any collada sdk, so i
have to manually find everything using an xml parser.

At the risk of asking too many noob questions, I'd better start digging
through the collada wiki some more. Thanks again.

On Wed, Jun 22, 2016 at 9:47 PM, Gaia Clary <gaia.clary at machinimatrix.org>
wrote:

> Hi, Khalibloo
>
> The collada format allows an optimization that only stores unique normal
> vectors. Then later the normal vectors can be referenced by using indexes.
> Also there can be more than one normal per vertex since Vertex normals are
> defined per face AND per vertex. Because of this the number of normals per
> vertex can be anything from 0 up to the number of faces which share the
> vertex.
>
> If you are sure that you found a bug, then please file a bug report and
> include a demo file that shows exactly where the data goes wrong. Then we
> will take care of this of course.
>
> BTW: If we talk about Blender's built in collada module, then please note
> that this is a functionality that was created in C++ and it uses the
> OpenCollada library.
>
> cheers,
> Gaia
>
>
> On 22.06.2016 21:06, Khalifa Lame wrote:
>
> Hello. I recently did some work on collada files exported from blender.
> From what I understood from the collada wiki from Khronos, the mesh normals
> xml node in the collada file should contain a trio of number values for
> each vertex. In other words, the mesh normals should have exactly the same
> number of entries as the vertex positions.
>
> This isn't always the case, however, when you inspect collada files
> exported from blender. Sometimes, there are more normals than vertices;
> sometimes, there are less. They hardly ever match.
>
> Is this a bug on blender's part? or is this intentional? if so, could
> someone please help me understand the logic behind it and how to read the
> normals reliably?
>
> This doesn't seem like a python question specifically, but if it turns out
> to be a bug, I'll have to write a python script to modify that behavior.
>
> --
> khalibloo®
>
>
>
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-- 
khalibloo®
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