[Bf-committers] Blender tangent space calculation

[Morten Mikkelsen]

Sorry for confusing you here but I think I found a better reference for you
since
you'll be needing the tangents too and you are not supposed to be building
them yourself.

The proper way to get the tangent layer can be seen in:

https://svn.blender.org/svnroot/bf-blender/trunk/blender/source/blender/editors/object/object_bake.c

do_multires_bake()

These are being fetched after the line:

float *pvtangent= NULL;


These are then read in the function flush_pixel() including the normal
which is fetched from there using multiresbake_get_normal()
which as you can see looks a lot like the GetNormal() function
I pointed you to in DerivedMesh.c.
Anyway, definitely use this file as your reference. I should have shown you
this one from the beginning.

If you need a free ultra simple welder there's one here -->
http://jbit.net/~sparky/academic/welder/
You specify how many floats you have per vertex and it will weld for you.



On Wed, Nov 16, 2011 at 5:32 AM, Eugene Minov <minov.eug at gmail.com> wrote:

> >
> > >If you can get hold of the dm
> > >(DerivedMesh)
> > >on the c side of things then I can show you how to get the correct
> normals
> > >and tangents
> > >and even help you get them welded should you want this.
> >
>
> Ok! Sounds good to me :)
>
> So right now I in progress of checkout latest svn sources and compile
> blender. (had problems with net)
> Then first of I'll try to create test version of python/C interface. I've
> not decided yet what names I'll use for it.
> And finally will be trying to implement it looking in DerivedMesh.c,
> I think that it's realy are a good example.
>
> If or when I have a problem, I'll be glad to use your help :)
> Many thanks for your kind cooperation!
>
>
>
> On Tue, Nov 15, 2011 at 10:41 PM, Morten Mikkelsen <mikkelsen7 at gmail.com
> >wrote:
>
> > I don't know anything about Python but if you can get hold of the dm
> > (DerivedMesh)
> > on the c side of things then I can show you how to get the correct
> normals
> > and tangents
> > and even help you get them welded should you want this.
> >
> >
> >
> >
> > On Tue, Nov 15, 2011 at 10:43 AM, Eugene Minov <minov.eug at gmail.com>
> > wrote:
> >
> > > Yes, I absolutely agree, hard faces obviously must be exported in the
> > same
> > > way how they seen in render.
> > > I think they can welds along with tangents.
> > >
> > > On Tue, Nov 15, 2011 at 9:01 PM, Morten Mikkelsen <
> mikkelsen7 at gmail.com
> > > >wrote:
> > >
> > > > There is no point in doing this unless you export the correct
> tangents
> > > and
> > > > normals. That is the ones
> > > > that were used to bake the normal map.
> > > >
> > > > I realize it blows that there is no API function to get the render
> > > normal.
> > > > So what you have to do is produce it yourself
> > > > like is done in
> > > > DerivedMesh.c<
> > > >
> > >
> >
> https://svn.blender.org/svnroot/bf-blender/trunk/blender/source/blender/blenkernel/intern/DerivedMesh.c
> > > > >
> > > > and
> > > > many other places as well.
> > > > An example in this file is the static function GetNormal() which is
> > used
> > > as
> > > >  a call-back function by mikktspace.c
> > > > and you can see how it uses the averaged normal if the face is set to
> > > > smooth and it uses
> > > > the face normal which it calculates itself if the face is set to
> flat.
> > > >
> > > > If you are going to make an api to export tangents I for one cannot
> > > > emphasize enough
> > > > that I prefer an all or nothing solution. Either do it right or don't
> > do
> > > it
> > > > at all.
> > > > The last thing we need is to introduce a new tangent space standard
> > > within
> > > > blender.
> > > > Either export the correct basis that was used for baking (this
> includes
> > > the
> > > > normal)
> > > > or don't try to do it at all.
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