I think that a better approach would be to allow multiple UV layers and
textures (and texture modes, like decals) on the model format. I understand
that right now FGFS only relies on the native AC3D loader, though AC3D is not
the only 3D format supported by OSG by any means. But there's no reason why
alternate lists of UV coordinates and textures could not be supplied along with
the basic mesh. The cleanest implementation would use a "FGFS native" model
format, but there's plenty of possible solutions, like a list of vertex indexes
along with the corresponding UV coordinates and material definition to
integrate the basic AC3D mesh, or several copies of the mesh with matching
geometry and differing materials... I suspect that OSG is not being used to its
full potential.
Alessandro
> From: vivian.mea...@lineone.net
> To: flightgear-devel@lists.sourceforge.net
> Date: Mon, 22 Apr 2013 13:34:36 +0100
> Subject: Re: [Flightgear-devel] Aircraft modellers - is a grain texture
> useful?
>
> Thorsten
>
> >
> > Okay, I've pushed an experimental version of a grain overlay texture for
> the
> > model ubershader to FGData. It affects Atmospheric Light Scattering only,
> > i.e. will be absent in the default rendering, which should make for easy
> > comparison.
> >
> > For lack of texture units, I had to take the rainbow coloring of
> reflections out
> > for the moment (again, only in the Atmosperic Light Scattering version). I
> > can't visually spot a difference, and in any case a 2d texture lookup call
> seems
> > an overkill for a simple 1d color table, so I plan to replace that by a
> function
> > eventually. As far as I can see and test, this shouldn't take any
> framerate
> > unless used.
> >
> > The grain overlay is configured pretty much like any other model effect in
> the
> > ubershader - a model specific effect file needs to set the flags, which
> are
> >
> > * grain-texture-enabled: does what you think it does, needs to be 1 to
> work
> > * grain-magnification : the texture magnification relative to the base
> texture
> > - I think values between 10 and 100 would work here
> >
> > The grain texture itself needs to be declared as n=14. The grain texture
> > should be largely transparent and seamless - I think unlike for the
> terrain
> > tiling artefacts are not an issue for artificial patterns, they actually
> occur.
> >
> > For a quick check, inserting the following xml code into
> Aircraft/Citation-
> > Bravo/Models/Effects/reflect.eff
> >
> > <texture n="14">
> > <image>Textures.high/Terrain/grain_texture.png</image>
> > <filter>linear-mipmap-linear</filter>
> > <wrap-s>repeat</wrap-s>
> > <wrap-t>repeat</wrap-t>
> > <internal-format>normalized</internal-format>
> > </texture>
> > <grain-texture-enabled>1</grain-texture-enabled>
> > <grain-magnification>50</grain-magnification>
> >
> > gives me this effect for the hull of the Bravo which is now re-painted
> using
> > the terrain grain texture at high resolution
> >
> >
> > http://users.jyu.fi/~trenk/pics/overlay.jpg
> >
> > Looks a bit like a military version...
> >
> > So, please play with it - it's basically down to how well the grain
> overlay can
> > be made.
> >
>
> Removing the rainbow effect spoils the highly polished aluminium effect on
> the b29 and the Lightning F1. It is also incompatible with AO effects. Will
> this all work with non-nVidia cards/drivers?
>
> The grain effect you proposed did not gain much if any support from
> developers. Do we need to go down this road? We are breaking more and more
> for minimal gains. Did we ever restore the wake effect on the Carrier with
> Atmospheric Light Scattering?
>
> I think something like the grain effect can already be achieved with the
> nmap tiling facility in the existing ubershader.
>
> Vivian
>
>
>
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