Matrix simulation for one time step (DC approach)

Hello all,

I have a small question. I have RGB data for 145 sky patches for one timestep that I retrieved from actual measurements. With this info, I would like to run a matrix simulation but for one time step only. So, I doctored a sky matrix file as follows (see pic below):

  1. The first line describes the ground patch (0 0 0)
  2. The rest of the lines describe the sky patches from 1 to 145
  3. Changed NCOLS to 1 instead of 8760 (don’t know if this actually does anything)

I was able to run the simulation but because the results look “typical” I cannot tell if this method actually works or it is just a coincidence. Is this a correct approach to accomplish the task?

Thanks for your help in advance!

Dear Rita,

I do not see anything wrong with your approach. As long as you make sure that you have calibrated absolute RGB values for the Tregenza patches, this seems perfectly right.
Also the NCOLS=1 is correct, as you only have one timestep. This is the same as you would get it from genskyvec for a single point in time. E.g. for an overcast sky with Eh=10.000lx (generated with “gensky 6 21 12 -c -B 55.9 | genskyvec -m 1”), the first lines then look like this:

genskyvec -m 1

3.41923758 3.57595243 3.98198724
8.48968408 8.87879419 9.88694492
8.11844221 8.49053699 9.45460281
7.91341889 8.276117 9.21583614



Just agreeing with David – this is exactly what comes out of genskyvec, and dctimestep handles a single time step without issue.


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Thank you very much for your answers, David and Greg!