Three-Phase Method _ Sky Vector - Daylight Matrix

Dear experts,

I am trying to learn three-Phase Method for Simulating Complex
Fenestration.

I have two questions of Sky Vector and Klems divisions of Daylight Matrix:

1) Sky Vector:
I am trying with Overcast Sky. I have done as following for Windows (I have
Ubuntu 14 now, but, I am checking the first steps done by Windows):

gensky 12 21 15 -c -B 0.55866 | perl c:/radiance/bin/genskyvec.pl -m 4 -c 1
1 1 > review/skies/12_21_15.skv

(I do not know if is good) So, I am sure that for each time during the year
it generates the same Sky Vector. However, I think that the "genskyvec"
calculation divided the sky in different parts in contrast with "gensky"
command that generate void brightfunc material. Therefore, the skyvector
does launch different values for each sky division? If I rotated my model I
get different illuminance date for only Sky Vector variable?

2) Klems divisions of Daylight Matrix:
When there is a definition of "kbin(Nx,Ny,Nz,Ux,Uy,Uz)", is it because for
each orientation there are some different values? I suppose that for each
orientation it uses the same divisions.

Excuse me, but, I am trying with a rotated model and I want to ensure that
I understand well the method. Sorry for the inconvenience. Thank you in
advance.
Your faithfully,
Urtza.

Hi Germán,
Thank you very much for explanation. Now I have more idea of the
Three-Phase Method.
I do not know how the sky rotate, but, I will check Sky Vector's
parameters.
Kind regards,
Urtza.

Germán Molina Larrain <[email protected]> escribió:

Urtza,

    REGARDING QUESTION 1.
    
The CIE Overcast sky is simetric and independent of the date and
location. That means that it does not matter if you rotate your model
and the sky or change the location and the date, it will always return
the same vector when fed into genskyvec.

Genskyvec approximate the sky as "finite elements" of constant Radiance.
I understand this is done using Ray-tracing. That means that each patch
(element of the sky vector) will have a different value that correspond
to this approximation.

   Finally, the sky vector does not depend on the model just as the
sun's position does not depend on the orientation of your apartment.
However, I understand it is possible to calculate a rotated sky vector.
This is faster than performing all calculations again with a rotated
model (i.e. if you rotate the sky clockwise, it is the same as rotating
the model counter clock wise).

REGARDING QUESTION 2.

   Klems divition is always the same divition. However, the direction
used to trace rays (for sampling and calculating the View matrix) will
depend on the orientation of the window. This is the same as saying that
the same camera will give you different images if pointing on different
directions.

   I hope I understood your questions and that my answers help

   Best,

   Germán

_Dear experts,

I am trying to learn three-Phase Method for Simulating Complex
Fenestration.

I have two questions of Sky Vector and Klems divisions of Daylight
Matrix:

1) Sky Vector:
I am trying with Overcast Sky. I have done as following for Windows (I
have Ubuntu 14 now, but, I am checking the first steps done by Windows):

gensky 12 21 15 -c -B 0.55866 | perl c:/radiance/bin/genskyvec.pl[1] -m
4 -c 1 1 1 > review/skies/12_21_15.skv

(I do not know if is good) So, I am sure that for each time during the
year it generates the same Sky Vector. However, I think that the
"genskyvec" calculation divided the sky in different parts in contrast
with "gensky" command that generate void brightfunc material.
Therefore, the skyvector does launch different values for each sky
division? If I rotated my model I get different illuminance date for
only Sky Vector variable?

2) Klems divisions of Daylight Matrix:
When there is a definition of "kbin(Nx,Ny,Nz,Ux,Uy,Uz)", is it because
for each orientation there are some different values? I suppose that
for each orientation it uses the same divisions.

Excuse me, but, I am trying with a rotated model and I want to ensure
that I understand well the method. Sorry for the inconvenience. Thank
you in advance.
Your faithfully,
Urtza._

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   2015-07-03 6:44 GMT-03:00 <[email protected]>:

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[1] http://genskyvec.pl