Hi,
On Wednesday, March 21, 2012 13:29:52 Renk Thorsten wrote:
> Mathias, maybe it's just me - but I have a serious problem understanding
> what you write. I have greatest respect for what you do, and I've seen some
> amazing things like the factor 50 speed increase of the geodinfo() call,
> but most of the time I have no idea what you're talking about. The above is
> symptomatic.
I agree that I am mostly very short. But this really is due to the lack of
time to do all step by step. Where I start explaning at that point where I
believe that it starts to get non trivial for others. So obviously I do not
hit that point ...
> Martin mentions you trying to integrate space-view into Flightgear. I've
> tried to google space view, but that returns mainly image collections and
> some company websites. So I have no idea what it is. As a result, I ask you
> to comment, because I want to know what you're trying to do and how it
> compares with what I do.
>
> Your anwers starts with reference to how to do scattering integrals outside
> the atmosphere. It assumes I know all the rest (how Earth is modelled, how
> scattering integrals are done inside the atmosphere, ...) and would just
> be interested in the technical detail how to do it from space. You then
> continue under the assumption that I had asked a highly technical question,
> detailing rendering with fog and scattering separated into the last step.
So what am I doing: I load a scenegraph model of the whole earth that, using
apropriate osg methods, aims toward a scalable scenegraph that is still able
to display high level of details once you are close to ground. This is just a
scenegraph object that is rendered. There is a whole lot of stuff contained
there to make that scalable, but for rendering this could just be considered
seperately then.
Take this and combine it with some technique that simplifies the skydome which
is only used today as a proxy geometry to get rendered pixels for the sky
shaders. And as such a way to high real existing dome/sphere that needs to be
rescaled and repositioned. You need to take care of this geometry for the
near/far clipping planes. All that could just be replaced by a simple fixed
screen aligned quad that has way less geometry and provides the same effect of
providing fragments for the scattering/sky shaders.
Once you have realised that scattering/sky is just the same than fog for
objects, it is clear that you want to do both in the same way/code. Which
simply leads to what I am talking about: Put that into a compositing step
where you combine the stuff that you get from rendered objects with the
scattering integrals. When you do this in a compsiting step, you get a lot of
possibilities to implement say shafts in the atmosphere where scattering
happens differently in directly lit areas than in inderectly lit ones.
Appart from that being a technology enabler for really nice visuals, you can
then omit ugly fog computations from the models. You can seperate different
stuff into different modules and untangle dependencies, which is good in its
own.
This is to a high degree really what Fred is working on, just with a different
detail in its usage. And in an other sense not that sophisticated than freds
approach for the material properties of the objects.
That's all you need.
I typically prepare a lot of things that are usually sensible and helpful for
its own but with such a final goal in mind. Once all is set up in place I just
need to grab into the black hat and pull out a white rabbit - in this case
this could be space flight. Totally independent of your request, but only
realizing stuff that is helpfull for its own and fitting together into some
bigger picture.
Does this help?
Mathias
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