[Radiance-general] Sky component only

[Thomas Bleicher]

On 23.09.2005, at 12:29, nick devlin wrote:

> Thomas,
>
> I used mkillum yesterday and bingo!!! got some better results, that  
> I am trying to validate.
> One question though, I just need to be certain that there is no  
> ambient light in my results.
>
> so to check, I am using the following for mkillum and then rtrace:
>
> mkillum -I -h -dp 2046 -ar 32 -ms 0.063 -ds .2 -dt .05 -dc .75 -dr  
> 3 -sj 1 -st .01 -ab 0 -aa .1 -ad 512 -as 256 -av 0 0 0 -lr 12 -lw . 
> 0005 -af scene2.amb scene2.oct < window.rad > mkwin2.rad

First I thought you should use ab > 0 for mkillum but this would add
the indirect contribution of nearby buildings, which is probably
not what you want.

I'd reduce the value of -dp (you don't have any virtual sources if
you're only interested in the sky) and increase the value of -ad
to get a very good sampling of the hemisphere (4096 or even more).

What's -ms for? Are you calculating paticipating media?

> rtrace -I -h -dp 2046 -ar 32 -ms 0.063 -ds .2 -dt .05 -dc .75 -dr 3  
> -sj 1 -st .01 -ae Zero_Ref -ab 0 -aa .1 -ad 512 -as 256 -av 0 0 0 - 
> lr 12 -lw .0005 -af scene2.amb mkscene2.oct < mk1.pts > existing3.dat

I wouldn't use the same ambient file for the mkillum and
the rtrace process. One (mkillum) contains the outside,
the other only the inside of your room geometry.

I don't think any of -sj, -st, -lr, -lw have much influence
on the calculation given your sky-only-setup.

I hope someone with more experience with mkillum and
rtrace can give you better hints. I'm just speculating
here.


Thomas