[Radiance-general] ambient resolution and memory

[Lars O. Grobe]

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.