[Radiance-general] Radiosity method implementation on Radiance

[Germán Molina Larrain]

Ok, I will have all that in mind!

I cannot give so many details now, but our idea is to get fast solutions
(trying to achieve interactivity) for design of interior spaces.

THANKS EVERYONE

German


2013/6/21 Greg Ward <gregoryjward at gmail.com>

> As I've noted when asked this question in the past, radiosity is faster
> for simple spaces with many interior reflections.  Complex spaces quickly
> become expensive to compute, and the meshing of them can be a nightmare.
>
> If you need to compute the illumination of an empty box, then anything is
> going to be fast.  If it's really, really important for you to compute
> empty boxes in a second or two, then radiosity is the way to go.  If you
> can wait 30 seconds, Radiance works, too.
>
> If you have a complex building to render with trees and sky, have fun
> doing it with radiosity!
>
> Cheers,
> -Greg
>
> *From: *Germán Molina Larrain <gmolina1 at uc.cl>
>
> *Date: *June 21, 2013 8:42:14 AM PDT
>
> *
> *
>
> Thanks for the answers Lars!
>
> I am thinking on "one-zone" simple scenes, without furniture. I was
> checking out Lightsolve <http://www.phil-seaton.com/#/lightsolve>algorithms, and for them, this approach seem to be working well. I am
> thinking on something similar, but not the same.
>
> Also, a friend of mine did some work on lighting simulations, and claimed
> that Radiosity was actually much faster than Radiance for those
> calculations.
>
> Anyway, lets see what others can say about this... I was aware of the
> hybrid-stochastic-deterministic capabilities of Radiance, but I am not sure
> what that exactly means, so I cannot say if this would be faster or not.
>
> THANKS!
>
> German
>
>
> 2013/6/21 Lars O. Grobe <grobe at gmx.net>
>
>> 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 ambient
>> 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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