[Radiance-general] rpict settings & open area relation

[Greg Ward]

Hi Jelle,

Yes, it definitely helps to know what we're talking about.  1000  
words/picture, at least!

The problem with the initial frames is that there aren't enough  
ambient divisions to find the few and tiny holes you have.  I  
recommend setting a much larger value for -ad at the beginning, and  
you can gradually relax this as you get more holes in your space.   
Just guessing, I'd say you need at least -ad 4096 for the initial  
frame, which will take 5 times longer to compute.  (I don't think you  
need to increase -as -- 512 should be enough.)

An alternate approach is to use illums in your openings with the  
outside distribution mapped to them, as described in Tutorial 0  
(Chapter 1 of RwR which is available online if you don't have it from  
<http://radsite.lbl.gov/radiance/book>).  The problem is that you'll  
probably want to switch at some point from using illum's to just open  
holes as you have them once you get a certain number and it stops  
paying off in the calculation.  With illum's, you can decrease -ab 3  
to -ab 2 and get the same result.

-Greg

> From: "Jelle Feringa / EZCT Architecture & Design Research"  
> <jelle.feringa at ezct.net>
> Date: June 9, 2005 3:56:46 AM PDT
>
> Dear Greg,
>
> I uploaded some images to: www.ezct.net/radiance/rpict_area_settings/
> Currently I'm using the following rpict parameters:
>
> rpict.exe -vf render.vf -ab 3 -ar 512 -ad 512 -ps 1 -as 512 -x 1500  
> -y 1500
>
> which is pretty basic, but as you'll see in the last frame is fast and
> artifact free, whereas there's little open area in the initial  
> frame, which
> of course leads to artifacts.
>
> I'm rendering out a animation which shows a cube dissolving in  
> space, each
> frame cuts out a certain area of the box, slowly leaving it to  
> dissolve.
> I figure having the open area parameter drive the Radiance  
> parameters would
> be a good approach, wouldn't it?
>
> Cheers,
>
> Jelle.