[Radiance-general] Radiosity method implementation on Radiance

[Germán Molina Larrain]

Hi Roland,

Thanks for the offering! Maybe in the (near, I hope) future I will ask you
for that! for now, I am working in some other stuff.

THANKS!

German


2013/6/21 Roland Schregle <roland.schregle at gmail.com>

> Hi Germán,
>
> aeons ago I hacked up a primitive radiosity thingy for RADIANCE in an
> afternoon to compare with our measurements for validation of diffuse
> interreflection. It's actually embedded in the rendering engine and may not
> compile with the current release anymore, but it might be worth looking at
> to give you some ideas on how (not?) to do it. As I recall, it used a
> standard relaxation method and a fixed quadrilateral mesh, so nothing fancy.
>
> Let me know if you're interested and I'll excavate that ancient artifact.
>
> Regards,
>
> --Roland
>
>
> --
> "END OF LINE" [MCP, 1982]
>
>
> On 21/06/2013, at 2:57 PM, "Lars O. Grobe" <grobe at gmx.net> wrote:
>
> > Hi German!
> >
> >> I am thinking on implementing a hybrid methodology between Radiosity
> >> method and Ray-tracing, for accelerating some calculations (by giving up
> >> accuracy, maybe)
> >
> > Did you think about in what use cases radiosity may be faster, and in
> > which it wouldn't? And are you aware of the "hybrid" rendering approach
> > used by Radiance? Especially the way that the ambient cache is working
> > as a means to accelerate the stochastic diffuse-indirect calculation
> > that a radiosity renderer aims at?
> >
> >> I think I can make algorythms to subdivide polygons into meshes,
> >> however, what I do not know how to do is:
> >
> > I think most of this is already happening when you are using the ambi
> > cache.
> >
> >> *1.- Calculation of View (Form) Factors:* I guess a straitforward way is
> >> to calculate them by randomly sending rays from one surface to the rest
> >> of them, but I do not know how to do that (or use octrees). (k/N would
> >> be the view factor Fij... where k is the number of rays that falled into
> >> j from i, and N the total number of rays sent)
> >
> > If you want to do this using scripts and the available tools, you could
> > step through all surfaces in a scene file. There are tools to do the
> > sampling available.
> >
> >> *2.- Render:* After I have the Radiosities of every polygon. How can I
> >> make a render? I guess I can use *vwrays *somehow, but I am not sure how
> >> to check which polygon am I "seeing", in order to use the calculated
> values.
> >
> > You can tell rtrace to output object names instead of radiance or
> > irradiance values. You can also get both the name of the object and its
> > radiance. This would even allow to add the radiance value of a scene
> > with -ab 0 and the precalculated "radiosity" value. Somehow what most
> > radiosity renderers do to achieve sharp shadows (they add a
> > raytracing-step for direct calculation).
> >
> > Still I have doubts that this can be faster than the current
> > implementation.... :)
> >
> > Cheers, Lars.
> >
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