> 1. You forget the fact that in the end this all gets applied to faces
> (triangles), and a point inside the triangle will have a value
> interpolated
> between the values of the three corners. I don't think that's a linear
> function anymore.
Then the fragment shader would never get correctly interpolated distances
as these are linear (?!)
> 2. Afaik light scattering and in the end fog isn't a linear function, so
> you
> get wrong results anytime an edge length is close to the value of the
> visibility distance.
Yes - which is why I left the non-linear fog function in the fragment
shader and moved the linear geometry computations into the vertex shader.
> You can pass any precomputed value from the property tree as an uniform
> just
> as you're doing with ground-visibility-m.
> Remember, an uniform has the same value for all vertices in the mesh,
> and then
> for all the fragments.
Yes, the angles between eye and sun are constants per frame throughout the
scene :-) So is hazeColor. My problem is not passing the value from the
property tree, my problem is getting it there - I'm not a C++ coder, I
have no clue where to look for gl_LightSource outside the shader, I have
no idea how (lat/lon/alt) property coordinates map into (x,y,z) in the
rendering process and I have no real idea how to make a vec3 out of
property values.
Which is why I asked for help in the first place...
* Thorsten
P.S.:
> The edge between fog/unfogged areas is too hard now, and it still doesn't
> match the horizon.
The edge is just as hard as it was previously - the functional form of the
fading hasn't changed. But just insert any distance function you like in
float fog_func (in float targ)
{}
and see what works best for your taste.
As for matching the horizon - it did in all my tests which were not at
sunrise/sunset - which combination of visibility-m ground-visibility-m and
ground-haze-thickness are we talking? I have just tried a few realistic
cases which I suspected to be problematic, but for instance a pathological
case with ground-visibility > visibility would probably not work,
ground-visibility > 25000 m starts to create other issues unless you
really open visibility into the 100 km range, I haven't tried extreme fog
like a 1 km thick layer with 50 m visibility. All I can say is that it
worked seamless in normal cases for me.
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