Hi all:
In the Klems_init.cal file, for south window (using kbinS), the Klems
coordinate is defined as:
z+: pointing to inside (that is, (0,1, 0) )
x+: pointing to West ( that is (-1, 0, 0) )
y+: pointing to Up (0,0,1)
This coordinate is consistent with the Klems coordinate system used in
WINDOW 6 (see this: https://dl.dropbox.com/u/15562376/coordinate.jpg). In
the figure, Klems coordinate system defines: x or xr points to (-1, 0, 0)
and y or yr points to (0, 0, 1).
However, if using this command to calculate view matrix:
$ rtcontrib < test.pts -f klems_int.cal -bn Nkbins -b *kbinS* -bn Nkbins -m
window_mat -I+ -ab 3 -ad 2000 -lw 1e-4 interior.oct > south.vmx
where, kbinS defines z axis in the Klems coordinate system as (0 1 0), that
is, pointing to room interior.
Thus, the bin number calculated by Klems_init.cal is actually based on z
hemisphere <https://dl.dropbox.com/u/15562376/coordinate.jpg> (the
hemisphere protrudes towards room). the bin number corresponds with
"Transmittance Front" in BSDF xml file. For example, ray direction (-1, -1,
0) (backward, ray travels from inside to outside room) hits the bin
58<https://dl.dropbox.com/u/15562376/bin.jpg>
defined in z hemisphere because the hemisphere protrudes towards (0 1 0).
But ray direction (-1 -1 0) hits bin
46<https://dl.dropbox.com/u/15562376/bin.jpg> defined in
z reverse (i.e., zr) coordinate because the hemisphere protrudes towards (0
-1 0) (towards outside).
When calculating Daylighting Matrix, it still uses Klems_init.cal and
kbinS, that is, z hemisphere coordinate system, therefore, Radiance seems
needing to use "Transmission Front", which is defined in z hemisphere. But
currently Radiance uses "Transmission Back" (from inside to outside), which
defined in zr hemisphere,
So, should we need to
(a) use "*kbinN*" (defining z axis of Klems coordinate towards (0 -1 0) )
and "Transmission Back" for south window, or
(b) use "Transmission Front" and *kbinS*?
I am very confused about this. Does anyone know the possible reasons?
Thank you !
Jia
···
On Sat, Oct 20, 2012 at 8:11 AM, Jia Hu <[email protected]> wrote:
Hi all:
I have a question about the bin number.
To calculate view matrix: (south-facing window)
$ rtcontrib < test.pts -f klems_int.cal -bn Nkbins -b kbinS -bn Nkbins -m
window_mat -I+ -ab 3 -ad 2000 -lw 1e-4 interior.oct > south.vmxkbinS uses the (0, 1, 0) as normal (pointing to inside room).
For a ray direction (-1, -1, 0), using klems_int.cal to calculate the bin
number, the bin number is about #57 (I did it manually).Klems_int.cal (download Klems_init.cal<https://dl.dropbox.com/u/15562376/klems_int.cal>)
seems use "z" hemisphere (see this figure:
https://dl.dropbox.com/u/15562376/coordinate.jpg). From the figure, we
can see "z" hemisphere points to the room (that is, the hemisphere is
located in the room) "zr" (z reverse) hemisphere is towards outside (the
hemisphere is outside the room).The possible inconsistency is:
(1) Klems_int.cal uses "z" hemisphere to calculate the bin number, for
example, for ray direction (-1, -1, 0), the bin number is #57 for "z"
hemisphere coordinate. (see this figure:
https://dl.dropbox.com/u/15562376/bin.jpg)(2) The "Transmission Back" data in the BSDF .XML is used in the three
phase DC method (see Greg's explanation<http://permalink.gmane.org/gmane.comp.graphics.radiance.general/2729>),
and thus the calculation is based on "zr" (z reverse) hemisphere , for ray
direction (-1, -1, 0), the bin number is about #69 according to the "z
reverse" hemisphere coordinate (see this figure:
https://dl.dropbox.com/u/15562376/bin.jpg).So my questions are:
(a) Given the ray direction, which hemisphere ( "z" or "zr" ) does
"Klems_init.cal" use?(b) whether the bin numbers (for the same ray direction) between
"Klems_int.cal" and BSDF .xml are inconsistent or not?(c) if they are using different bin numbers, how to handle ViewMatrix *
BSDF in the calculation?Thank you in advance,
Jia