[Radiance-general] ambient resolution and memory

[Jack de Valpine]

Hi Lars, Greg, and Carsten,

First off. Carsten, it is always great to get you input and thoughts on 
Radiance related topics! So please please let us know your thoughts any 
time.

On the thread at hand. I just wanted to pass along to Lars. That after 
Greg's comments regarding the source occluder caching and 
instancing/meshes, I decided that I needed to do an experiment. Like 
you, we make heavy use of instancing to manage assembly of complex 
scenes from component parts. This is so much so that whole buildings 
will end up being an instance (even if though there is only one). From 
the standpoint of scene management this has been quite helpful. However 
after Greg's comments, I went back and recompiled a current scene making 
it "flat" (eg, no instances). All, I can say is WOW! The computation 
time was reduced significantly! So, now I am looking at the best way to 
add an option to produce flat scenes and make more sparing use of 
instancing in our scene management tool.

-Jack

Lars O. Grobe wrote:
> Hi Greg!
>
>> Just finished with the Radiance workshop, so catching up on e-mails.
>
> I am curious to hear about it, will there be a documentation cd 
> available again? Hope ou had a nice time.
>
>> The "glow" type with an effective radius still illuminates the scene 
>> correctly.  Base your radius on the distance over which you expect 
>> your sources to be important.  Past that distance, they will be 
>> considered as "indirect" sources.  One important caveat:  the smaller 
>> and brighter they are, the more artifacts you will see from them if 
>> your radius is too small.
>
> I will hide it behind an illum. The configuration is as follows: I 
> group my (artificial) light sources and define one illum sphere per 
> groups of sources. That way, first I will have much less sources in 
> the indirect calculation, and second avoid these artefacts. Actually I 
> was not aware about the advantage of using glow instead of light 
> modified sources. The actual sources are small oil lamps, which I 
> expect to be effective only indirect a groups - the room is too large 
> compared to the lamps.
>
>> Another tip to reduce calculation time if you are using a recent 
>> version of Radiance (3.6 or later) is that large surfaces in the main 
>> octree will be tracked in the shadow cache.  Neither instances nor 
>> meshes will work as obstructors, so if you must instantiate geometry, 
>> leave at least some large occluders in the main octree to help in the 
>> shadow cache.
>
> ;-) Do you know my model that well? Thank you, this may help a lot. My 
> model is build up in a hierarchic way, with the top elements often 
> being instances. Maybe I should even accept overlaps just to get some 
> occluders without changing the model too much. If I keep the visible 
> geometry in instances, but have some large faces in the main octree a 
> approximations to these main elements, which are invisible because 
> completely covered by the instances' geometry, should I expect some 
> performance gain from the shadow cache?
>
>> It's a curious idea.  I'm not sure whether or not it will help, but 
>> I'd love to see the results.
>
> I will try it. I think it highly depends on the point of view related 
> to the scene, but in my case it may help (important viewpoints all in 
> central hall-like room, window openings mainly in adjacent 
> aisles/galleries etc).
>
>> There is no such hack.  It's not really physical, is the problem.
>
> Yes, but it is useful to exclude patterns and textures from the 
> ambient and stay with the base modifier.
>
>> One other note -- you might try setting -ar 0 in your case.  If you 
>> have really large and small geometry that require enormous -ar 
>> settings, you may be better off without it.
>
> I was at around 2000, I will try 0 now.
>
>> ground plane from the indirect calculation with a -ae option.
>
> There is none. I use the sky/ground-sphere only. It is the building's 
> dimensions related to its details.
>
> Thank you for your help! CU Lars.
>
>
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