[Radiance-general] sharing the ambient cache

[Jack de Valpine]

Hi Greg and Rob,

The strategy that we have always used is based on John's recomendations 
in RwR. For example:

parameter
	first pass (overture at 64 or 128 pixels)
	second pass (whatever your next resolution is)
-ad
	1024
	512 (1/2 of first pass)
-as
	512
	256 (1/2 of first pass)
-aa
	.15
	.25


In RwR, John does not recommend changing the other ambient parameters. 
However, I am intrigued to hear that Greg indicates that it would be ok 
to reduce -ar as well as -ab. It would be interesting to run some test 
and determine what good reduction parameters would be.

Now, we use the parameter reductions mainly for "pictures." I am 
interested to consider what kind of parameter reductions would work when 
moving from a tight grained high -ab quantitative simulation to 
something that could still use the ambient cache for producing 
"pictures," which is more clearly what Rob is thinking about.

-Jack

Greg Ward wrote:

> Hi Rob,
>
> Jack de Valpine or John Mardaljevic may know more about this than I  
> do, as they have experience using different ambient settings in  
> different runs, whereas I tend to stick with the same settings I  
> start with.  In general, it's safe to run with reduced ambient  
> settings in subsequent renderings when you share an ambient file.   
> Specifically, it's OK to relax the -ad and -as settings, and -aa and - 
> ar as well.  You can reduce -ab (though -ab 0 won't use the ambient  
> file values at all), but I wouldn't recommend changing -av or -aw.   
> (There is no speed advantage to doing so, anyway.)
>
> -Greg
>
>> From: Rob Guglielmetti <rpg at rumblestrip.org>
>> Date: December 21, 2005 3:14:25 PM PST
>>
>> Hi folks,
>>
>> I should know the answer to this, but I don't.  Let's say I have a  
>> script that performs some numeric analysis of a scene (rtrace) and  
>> then does some renderings as well.  I typically crank up the  
>> settings quite a bit for rtrace, but relax them a bit for images  
>> (usually).  My question is, can the rpict process(es) safely use  the 
>> existing ambient cache left over from the high-accuracy rtrace  run?  
>> Could running the rtrace at lower accuracy settings degrade  any of 
>> the previously cached values?  Just curious.
>>
>> - Rob
>>
>
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