What does the "-c " property of the honeybee_radiance_command.options.rfluxmtx module control? The documentation here and the manual of rcontrib give the following description:
The -c option tells rcontrib how many rays to accumulate for each record. The default value is one, meaning a full record will be produced for each input ray. For values greater than one, contributions will be averaged together over the given number of input rays.
Does this mean that, for example, if I set -c to 1 (default), all the sample rays will be recoreded, but if I set -c to, say, 2, only the average radiance value of every two rays originating from the sender plane will be recorded?
After digging into the source code of Radiance, I found that -c is passed to a variable accumulate in Radiance (here). This accumulate parameter affects the number of rays to trace (here), and finaly is used to average the results (here).
I wonder then what is the point of defining the -c parameter, now that I can increase the number of rays by other parameters? Is it for reducing memory usage?
Unless you are using one of the 3-6Phase methods, the value of -c should remain 1. The -c parameter, in non-pass through mode, is a means to control Monte-Carlo surface-sampling for calculating flux-transfer between two surfaces. In the case of the standard daylight coefficient method (aka Two-Phase, Annual recipe in HB[+]), rays originate from grid points that are proxies for real world illuminance sensors and terminate at geometry-surfaces or the sun/sky. So the notion of surface-surface flux transfer does not apply.
Regards,
Sarith