Rfluxmtx -x and -y input options

#1

Hi all,

I was trying to run simulations for multiple test points but only the results for one test point was outputted from rfluxmtx. I then figured that setting the input value to -y as the number of test point worked.

So my questions are:

  • is it true that -y must be set as the same number of test points? I read the documentation from rtrace but still was not sure
  • I did not set value to -x. What’s the default value? And how -x is useful?

I don’t know too much about the fundamentals of ray tracing. So some simple explanation can be useful. Thanks everyone!

#2

Hi Zha,

It’s difficult to answer your questions without more information about your problem. The -x and -y options serve multiple purposes in rcontrib, which is called by the pass-through mode of rfluxmtx. If you share your command, input file, and output, this would be helpful.

If you do not specify the -y option, then rfluxmtx should read until the end-of-file on input, and produce results appropriate to its other parameters and inputs. If you use rfluxmtx in sampling rather than pass-through mode, then the -x and -y options are ignored and have no effect.

#3

Dear @Greg_Ward

Thank you very much for your reply.

Here is the command:

rfluxmtx -n 8 -y 5 -aa 0.25 -ab 3 -ad 5000 -ar 16 -as 128 -dc 0.25 -dj 0.0 -dp 64 -ds 0.5 -dr 0 -dt 0.5 -I -lr 4 -lw 2e-06 -c 1 -ss 0.0 -st 0.85 - rfluxsky.rad glz.mat glz.rad opq.mat opq.rad < testpts.pts > normal.dc

The file testpts.pts contains:

4 0.01 1.35 0 1 0
4 3 1.35 0 1 0
4 3 1.35 0 -1 0
4 3 1.35 1 0 0
4 3 1.35 -1 0 0

I used to set y =1, then the normal.dc only output NROWS=1. The problem would only be solved if I set y = 5, which normal.dc contains NROWS=5.

Any comments, please?

Not related to the question above, I am wondering for gendaymtx module, why setting the option −c does not change the results?
For example:

gendaymtx -O0 -r 0.0 -m 1 -v -c 0.2 0.2 0.2  CAN_AB_Calgary.Intl.AP.718770
_CWEC2016.wea > total.smx

and

gendaymtx -O0 -r 0.0 -m 1 -v -c 1 1 1  CAN_AB_Calgary.Intl.AP.718770
_CWEC2016.wea > total.smx

both will produce the same results. So I am wondering if this is expected behavior? Only by changing the ground color option -g will be able to change the results.

Thank you for your help and for developing the software!

S

#4

If you set -y N, then rfluxmtx will stop reading its input after N sample points. If you don’t set -y at all, then it will read to the end of the sample points. Also, your -aa, -as, -dt, and -dc settings are ignored, as they are not compatible with rcontrib.

Regarding the gendaymtx -c option, this should affect your sky patch colors, so the only possibility I can think of is that something is wrong with your other matrix. If normal.dc has zero coefficients for the sky, then the color of the sky would make no difference.

#5

Dear @Greg_Ward,

Thank you for your reply.

The immediate output from gendaymtx (i.e. total.smx) remained identical even when I change the color option. I don’t think it is affected by normal.dc.

Thanks,

S

#6

Oh, that does seem like an error. Can you share the WEA file you gave it? My quick test shows that the -c option is doing what it should do.

#7

Dear @Greg_Ward:

Ahh, sorry I did not check them thoroughly. It appeared that the first few sets of values are identical but not all of them are identical… Anyway, here is the file: https://github.com/zha/public/blob/main/CAN_AB_Calgary.Intl.AP.718770_CWEC2016.wea

Another question about this is: If I use the default luminous efficacy of 179, should I just use the default color option (−c 0.960 1.004 1.118)?

Thank you very much.

S

#8

Yes, I would generally leave the -c option alone, and it’s not a good idea to set it so the sum of RGB components is very different from 1.0 unless you have some specific thing you are testing. (Technically, 0.265R + 0.670G + 0.065*B should be 1.0)

The first several sets of value in the gendaymtx output will be the same, as you are looking at the first row, which is the ground.

#9

Dear @Greg_Ward

May I please ask why the default is not 1 1 1? Because this will make 0.265 R + 0.670 G + 0.065*B perfectly equal to unity?

Also, when the RGB color options are identical (or near-identical), the RGB irradiance output from gendaymtx will also be identical, so in this case, can I just take either one of the three values and carry on with the rest of my calculations?

Thank you very much,

S
,

#10

The only reason the default is not 1 1 1 is to give the sky a slight blue tint, which is more accurate if you are performing a color calculation. If all your surfaces are gray, then you can set -c 1 1 1 and just use any channel for the result as you suggest.

#11

I see! Thank you very much @Greg_Ward

Happy holidays!