[Radiance-general] 3-phase method daylight matrix

[Greg Ward]

Hi Eleanora,

I'm not sure I'm understanding your question fully, but you can have multiple *receivers* in the same file to generate multiple matrices using rfluxmtx.  However, if you wish to use those receivers (i.e., your window surfaces) as *senders* in a subsequent run (i.e., for the exterior daylight coefficients), then you must have them in separate files for multiple runs of rfluxmtx.

It is probably poor program design on my part, but currently, rfluxmtx ignores the materials in a sender file, and just puts them all together as a single "average" surface.  This gives unintended results if you give it two well-separated windows of different orientations, and this is possibly the source of your errors.

For optimal efficiency using rfluxmtx for 3-phase, it is better to have separate files for your different elevation windows, with different modifiers in each.  For example, you might have:

east_windows.rad	(using "east_window_mat" to modify all the surfaces)
west_windows.rad	(using "west_window_mat")
south_windows.rad	(using "south_window_mat")

This would allow you to do the necessary 3 separate runs of rfluxmtx to compute the contribution from each elevation's windows for the external daylight coefficients.  Then, you could have a combined "receivers.rad" file that contains the following single line:

!xform east_windows.rad west_windows.rad south_windows.rad

You would give this one-line file to a single run of rfluxmtx to compute the three interior flux transform matrix for your sensors.

Does this help?

Cheers,
-Greg

P.S.  I will see if I can add a warning message for sender files with multiple modifiers, as this seems such an easy mistake to make!

> From: Eleonora Brembilla <E.Brembilla at lboro.ac.uk>
> Subject: [Radiance-general] 3-phase method daylight matrix
> Date: March 12, 2015 10:56:17 AM EDT
> 
> Dear all
> 
> I have a couple of questions about the 3 phase method, I haven’t used it much before so I’d like to be sure of what I’m doing.
> 
> 1. I have a multi aspect room, so I divided the windows in two groups, depending on their orientation, each group with its own modifier (is it alright even if they are in the same file?). In this way, the first run of rfluxmtx automatically produces two view matrices. The second run, for the daylight matrix, works well either if I use the same single file with all the windows in it or if I create two separate rad files for the two orientations, but the final illuminance results are somehow different (lower for the first option, higher for the second). I am carrying on with the two separate files, because of something reported in the older version of the 3-phase method tutorial about this, but I’d like to know if it’s the right way to go.
> 
> The ambient parameters I’m using are:
> -ab 12 -ad 50000 -lw 2e-5	(for the view matrix)
> -ab 2 -ad 5000 -lw 2e-4		(for the daylight matrix)
> 
> Also, when at the end I have one illuminance file per orientation, is it correct just to add them together using the rmtxop addition?
> 
> 2. As well as the transmission matrix, all the other matrices in the rmtxop multiplication can be substituted if I am changing only one condition, right? e.g. if I’m testing different grid resolutions I am changing only the view matrix and if I use different time steps I’ll change only the sky matrix.
> 
> Thanks a lot in advance!
> Eleonora