Radiance Convergence - Simulation parameters

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-as, -dj, -dp, -dt, and -dc have no effect in a daylight coefficient simulation with rcontrib, so you can ignore those.

The parameters you're using look similar the parameters I recommend for the interior view matrix of a three-phase calculation, which was determined with convergence testing on the BRE-IDMP dataset.For convergence testing I recommend taking roughly 1% of the test points and running simulations with varied parameters. The points chosen should be some of the more challenging, further from the window and in corners.

The critical parameters for matrix generation (with glow materials as light sources) are usually -ab, -ad, and -lw. I'd recommend something like this:

for ab in 6 8 10 12 ; do
for ad in 1024 4096 16384 65536 262142 ; do
for lw_power in 1 1.5 2 2.5 3 ; do
lw = 1 / (ad^lw_power)

rcontrib ... -ab $ab -ad $ad -lw $lw ...  < fewpoints.txt > result_${ab}_${ad}_${lw}.mtx

done; done; done

Then you can either compare the difference in matrix values, or you can generate a test set of sky vectors (sunny morning, sunny noon, sunny evening, overcast, etc.) and compare illuminance results between the runs. Then if thee's a big jump between ab 6 and 8, a small jump between 8 and 10, but only a minor difference between 10, and 12, you're okay with -ab 10. You could go back and test -ab 9 in a second run, if you want to be superbly optimal. If there's still a sizable jump between 10 and 12, then maybe run some more with -ab 14 and 16. I find it helpful to plot results, that way you can see if things flatten out, and you can also recognize noise (which will be apparent with low -ad and -lw runs)

You might also want to time the simulations, so you can estimate the full run length (which is semi-linear with number of simulation points).

And finally, rfluxmtx (which calls rcontrib in the background) has simplified the process of daylight coefficient simulations greatly. You might want to look at Sarith's tutorial and consider using rfluxmtx instead of rcontrib. https://www.radiance-online.org/learn...

It would be helpful if you could share a bit about the model. What is relationship of the points of interest to the transfer matrix surfaces? Is there even a T matrix? In other words, is this a single phase (some folks call it two-phase, mmm hmm), where you are tracing rays from the POI directly thru fenestration and to the sky, or is it three-phase? If the former, how complicated is the window interface geometry? If it's complicated, you may want to consider the three phase method. My gut reaction is that you have some complex geometry at the perimeter and so even with the aggressive sampling settings you have there for the view matrix, you're getting a lot of variation.

Hi!

I still struggle to find the best set of parameters for lighting simulation! But, yours seem quite "high", so I would expect your results to have converged already, thus my first next guess would be to simplify the geometry.

I am not sure I am reading your facade properly, but if you want to use the 2-Phase Method, I would keep the windows the same, without removing details. The 3-phase method is better when your facade is optically complex (i.e. when there will be a lot of bounces and scattering on when the light goes through your window), not when the shape of the window is complex. Your facade seems to match better the latter case...?

Now, I do not think you need all those details in your geometry. You are calculating the illuminance on a grid and thus you can avoid the trouble of dealing with corners and other complexities. I might be wrong, but I think all those details in your railings may be "absorbing" part of your high parameters. That is, lots of rays get stack bouncing around them without really improving the results on your grid. Maybe try simplifying those and see if you get more stable results.