[Radiance-general] multi-processor rendering

[Greg Ward]

Well, this feature is not exactly "new" anymore, but rad didn't always manage rpiece for you.  I added this facility back in 2011.  It should work the same if there is only one view in the file as when you use the -v option to specify a single view.

Cheers,
-Greg

> From: Christopher Rush <Christopher.Rush at arup.com>
> Date: October 7, 2016 6:20:36 AM PDT
> 
> Great suggestion. I will test. I think I had tried the -N option with rad but didn’t find it using multiple processors when just one view is in the .rif file (if my memory serves correctly). I didn’t think to try specifically calling for just the one view along with the -N option.
>  
> -Chris
>  
> From: Greg Ward [mailto:gregoryjward at gmail.com] 
> Sent: Thursday, October 06, 2016 12:32 PM
> To: Radiance general discussion
> Subject: Re: [Radiance-general] multi-processor rendering
>  
> Hi Chris,
>  
> If you would use -ps 1 on the command line of rpiece because you are doing specular sampling or setting -dj .7 (or whatever) to calculate penumbras, then your rtrace command will be just as fast as rpiece.  The main advantage of rpiece on large images is the image plane sampling it does.  Setting -ps 4 (the default) samples only 1 in 16 pixels to start, then subsamples in areas where it detects something going on.  This can be a big time-saver, especially in scenes with a lot of smoothly shaded areas.
>  
> The rad command will run rpiece for you if you set the -N option to the number of processes and the -v option to specify a single view you want rendered.  This is a much easier way to operate, and should be entirely reliable under Mac OS X and most versions of Linux.  You can run your own comparison against rtrace with vwrays and report back.  I'd be interested to hear what you find.
>  
> One more thing about rtrace is that it doesn't put your view in the header of the output, so if you want to use that output with programs that need the view, you will have to re-insert it.  The latest version of getinfo makes this a little easier, e.g.:
>  
>                 vwrays ... | rtrace ... | getinfo -a "VIEW= $view" > view1.hdr
>  
> Cheers,
> -Greg
> 
> 
> From: Christopher Rush <Christopher.Rush at arup.com>
> Date: October 6, 2016 9:08:37 AM PDT
>  
> Several years ago I tried out rpiece but found it wasn’t always reliable – at least not on the system I had been using. I found this following vwrays and rtrace command sequence to work well to get around this. This is for creating a few renderings of a single static scene (for example electric lighting, or single daylight condition). Of course there would be additional ambient parameters on the command line. So I have two questions in addition to opening this to general critique:
>  
> 1. Has rpeice changed much over the past few years, and would it have any processing speed benefits if I were to try it again?
> 2. Would using rcontrib offer any processing speed benefits? (I started that way but then realized I should gain speed using the ambient file for rtrace)
>  
> Example successful command sequence using 6 processors:
>  
> view1="-x 4096 -y 2160 -vf view1.vf"
> vwrays -ff $view | rtrace    -w -n 6 -af scene.amb -ffc $(vwrays -d $view) scene.oct > view1.hdr
> vwrays -ff $view | rtrace -i -w -n 6 -af scene.amb -ffc $(vwrays -d $view) scene.oct > view1-i.hdr
>  
>  
> Thanks for all feedback.
> Chris
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