[Radiance-general] Instances

[Lucio Boscolo]

Hi Greg,

Thank you so much for your detailed answer (and sorry for being late again exploring it). 

-aa method is a good one, but I am a little concerned this will impact a lot on rendering time in a scene like mine in which many ab are required and a very high number of rays (it is a comparison between shading systems to work out transmittances).

The -PP option seems to be what I need, but I am not sure I understand it. Please tell me if the following is correct.

I start an rpict (or rtrace) with a -PP namefile option.

I start other rpict or rtrace wit -PP namefile (the same) and they will share memory (ram?)

Ambient file instead will be shared by using -af and the same ambient file for all the processes.

Is this correct?

I believe -S is not needed with the -PP option, am I right?

Can I share with -PP between rpict and rtrace processes?

Thank you for your help, one of my colleagues run into the same issue today, so it would be very good if we manage to solve this! 

Have a nice day!!!

Lucio 

-----Original Message-----
From: Greg Ward [mailto:gregoryjward at gmail.com] 
Sent: 23 December 2010 17:33
To: Radiance general discussion
Subject: Re: [Radiance-general] Instances

Hi Lucio,

If you are executing in parallel on a shared memory machine, are you using the -PP option to rtrace (or rpict)?  This can help to reduce memory, especially on jobs where you are loading in a substantial ambient file to start.

Another approach is to abandon ambient caching entirely, which makes sense in scenes where you have a lot of important detail, but what's most important about it is the aggregate behavior.  I think your problem falls into that category.  Unfortunately, whatever -a* settings you have worked out will have to be rethought when you do this.  I should have a good guide for how to set these parameters, but you basically start by setting -aa 0, at which point -af, -ar, and -aw settings become irrelevant (no caching), and the -ad and -as settings should be changed.  You also should look at the -lw and -lr settings, because they will have a strong influence over how deep the ray tree is explored.

Axel Jacobs offers a brief treatment of these settings on page 12 of his rtcontrib tutorial, currently linked at:

	http://luminance.londonmet.ac.uk/learnix/docs/rtcontrib_lesson.pdf

It's probably worth a try.  I use -aa 0 routinely when modeling blind systems in mkillum, for example.

Best,
-Greg

> From: Lucio Boscolo <Lucio.Boscolo at arup.com>
> Date: December 23, 2010 4:18:25 AM PST
> 
> Hi Lars, 
> 
> Sorry again for late answer.
> 
> I think it is a memory problem because I monitored it with top and memory is quickly reducing and as soon as it goes under 100 MB or so (when it probably starts swapping to the HD) processors use drops to 0.something %. I've got 8 GB memory and ambient files are big up to 1.5 GB (very high settings). In the worst case the octree is 600 MB.
> 
> Unfortunately the detail is all in a shading device (it is actually a transmittance study) so, no chance for using ambient exclude. And there are no overlapping geometries in the single instances and the instances replication is done by xform using the bounding box for spacing. Also care has been taken in taking away vertical faces at the boundaries to avoid overlapping surfaces. 
> 
> So what I understand from this is that if rpict loads ambient files in memory as well as octrees, in the worst case I will have for each rpict calculation 1.5 + 0.5 + some work memory in use (I don't know how to quantify this). As I cannot run more than 2 processes, the work memory is probably bigger than  [7.5(available ram  memory) / 3 (max processes before it runs out of memory)] -[1.5+0.5] = 0.5 GB, which makes sense to me. 
> 
> What do you think?
> 
> As Jack was saying I should have organized the model better, but still is good to understand what happened for future use.
> 
> Thanks for all your help and Merry Christmas to you both and to all the radiance community :-)
> 
> Lucio Boscolo Mezzopan

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