Dear Kyle,
I downloaded the file that was in the link you attached for rendering hdr sky images. I tried it with two of my images, the first was a clear sky and the other one was an overcast sky.
With the overcast sky I didn't had any problems, it rendered fine, although the clear sky image render didn't come out well. There are two issues: the first is that in the HDR images the sky appears really dark, and in the TIFF image the sky looks good but the ground disappears.
Could you give me some tips to improve the clear sky images? Have you had this problem when dealing with a clear sky render?
This is the link where you can see the results: https://www.dropbox.com/sh/ujhiskn9ohks3vt/AAAjkOyAis6_MfCEHfXwwalea
Best,
M. Beatriz Piderit M.
Arquitecta UBB, MA, PhD UC Louvain
Departamento Diseño y Teoría de la Arquitectura
Universidad del Bio-Bio Concepción, Chile
···
El 01-07-2014, a las 19:10, [email protected] escribió:
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1. Re: HDR Sky Camera @ LBNL's Flexlab (Kyle Konis)
----------------------------------------------------------------------
Message: 1
Date: Tue, 1 Jul 2014 16:10:29 -0700
From: Kyle Konis <[email protected]>
To: Radiance general discussion <[email protected]>
Subject: Re: [Radiance-general] HDR Sky Camera @ LBNL's Flexlab
Message-ID:
<CAAzVHq2LfEF7k1q2Asexzh4Du-jeTJd_pfqB4SUZ4BO1x=hiXQ@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"Following up here, (and on the referenced thread from about a year ago), i
did succeed in rendering some simple Radiance objects with HDR skies.I have uploaded an example video here with the LBNL Skycam images (June 21,
2014 until about 10:40 AM) which was all I could process during the world
cup match:
http://performance-and-form.com/projects/rendering-digital-objects-with-high-dynamic-range-hdr-sky-images/Thanks are due to Coralie Cauwerts for corresponding to provide me with the
proper .cal file for mapping hemispherical (rather than spherical) images.The skies are used to render a chrome sphere sitting on a pedestal. You can
tell it is not a real object because it is outside for several hours and no
birds sit or poop on it. (Good luck HDR Skycam ! )I have zipped all the files used to make the video and put them on the page
for download, as well as a few experiments i have made in manipulating
surfaces (either transmission or shading) in response to sky data from
Portland, Oregon using a Canon A570 with Stereo Data Maker used to automate
bracketed image acquisition (i have a plan to post the details for that, as
it is a very low-cost < $80 approach and will get to it).let me know (offline) if there are issues downloading or executing the
files,best,
-Kyle
-----------------------------------------------
Kyle Konis, AIA, Ph.D
Assistant Professor
School of Architecture, WAH 204
University of Southern California
Los Angeles, CA 90089-0291
http://arch.usc.edu/faculty/kkonis
-----------------------------------------------On Tue, Jul 1, 2014 at 8:52 AM, Christian Humann <[email protected]> > wrote:
Hi Joe,
Thank you for the references.
The HDR image by default is co-planar with the x and z axis with its
surface normal pointing in the negative y direction. You'll need to
translate the image so that its surface normal is pointed down along the
negative z axis and rotate it so that North is up when looking up towards
zenith.The groundglow description is actually not necessary and has no effect. If
you wanted to define the ground for inclusion in a scene you could use the
following:void glow groundglow
0
0
4 .15 .15 .15 0 #(.15 .15 .15 = RGB values for the ground material)groundglow source ground
0
0
4 0 0 -1 180I too have been getting lower values than the measured global horizontal
illuminance. I think the suggestions made made by Rob and Greg about using
mksource and adjusting the subtended angle of the solar source may be the
solution. Not sure yet how to implement the latter but I will certainly
keep you posted.Cheers,
ChrisOn Jun 30, 2014, at 10:26 PM, Joe Smith <[email protected]> wrote:
Hi Chris,
Thank you very much for your reply, especially for reminding me the
conversion of the unit between foot candela and lux!May I ask the following questions?
1. why the hdr fisheye image needs to be rotated along x axis for 90
degrees and along z axis for 180 degrees? using the fisheye.cal file as
reference when defining the colorpict "skypict"?2. why "skypict is used as a modifier to define the "glow" material
"groundglow"? I thought usually this position is set as "void"Using your approach, I tried some other hdr image provided by your
project, and it seems the global horizontal illuminance is always
underestimated as compared to the one reported in the csv file.rubbing my head about this issue, and advices are greatly appreciated!
Regards,
JoeOn Tue, Jul 1, 2014 at 3:06 AM, Christian Humann < >> [email protected]> wrote:
Hi Joe,
The global values in the CSV file are in footcandles so you will need to
multiply them by 10.76 in order to get Lux.Also, you'll need to add a source description for the sun in order to get
the solar contribution as the camera sensor can not capture the intensity
of the sun for the HDR image. Essentially the HDR image allows you to get
a close approximation of the global diffuse value. I use gendaylit (see
below) to generate the sun and sky scene. You can get the altitude,
azimuth, direct-normal-illuminance and diffuse-horizontal-illuminance from
the CSV file (be sure to multiply the latter two values by 10.76 to
translate them from footcandles to Lux for input into Gendaylit). Also be
sure to adjust your 'rtrace' results by dividing by 10.76 to get
footcandles if you want to compare to the global-horizontal-illuminacne
readings in the CSV file.########Sun and Sky scene -----> global.rad
!gendaylit -ang 45.41 85.92 -w -O 0 -L 80463.28 19916.76 | xform -e -rz
0
void colorpict skypict
11 red green blue 140621_1530.hdr fisheye.cal fish_u fish_v -rx 90 -rz 180
0
0skypict glow skyglow
0
0
4 1 1 1 1skyglow source sky
0
0
4 0 0 1 180skypict glow groundglow
0
0
4 1 1 1 0groundglow source ground
0
0
4 0 0 -1 180
#########
# 3. the cmd.sh file
oconv ./global.rad > ./scene_empty.octecho '0 0 0 0 0 1' | rtrace -I -h -w -ab 1 -oov ./scene_empty.oct >
./results_position_irradiance_RGB_wm2.txtcat ./results_position_irradiance_RGB_wm2.txt | rcalc -e
'$1=179*(0.265*$4+0.670*$5+0.065*$6)/10.76' > ./results_illuminance_lux.txt
##########When I run the above I get a global horizontal illuminance value from
'rtrace' of approx. 6900 footcandles. The photometer gave a reading of
7176 footcandles.I'm still working my brain around all this as well and hope that these
discussions will foster a better understanding of how to use the HDR images
for the highest level of accuracy possible.Hope this helps.
Best,
ChrisOn Jun 28, 2014, at 10:06 AM, Joe Smith <[email protected]> >>> wrote:
Hi, I found 2 references and did a test to generate HDR image-based
rendering, steps are explained below.But I'm still rubbing my head to understand how the Cartesian coordinates
or the postion vector of a point on the sky is transformed as UV
coordinates of the fisheye image as shown in the "angmap.cal" file. So,
advices are greatly appreciated!Thanks!
JoeReferences:
1. Debevec, P. (2002). Image-based lighting. IEEE Computer Graphics and
Applications, 22(2), 26-34. doi: 10.1109/38.988744
2. Au, P. Y. P. (2013). HDR Luminance Measurement: Comparing real and
simulated data. (Master of Building Science Thesis), Victoria University of
Wellington.Steps:
Step1. prepare the following 6 files and put them in the same folder#### 1.1 geom.rad ################################################
red_plastic sphere ball
0
0
4 2 2 0.5 0.5steel sphere ball1
0
0
4 2 -2 0.5 0.5gold sphere ball2
0
0
4 -2 -2 0.5 0.5white_matte sphere ball3
0
0
4 -2 2 0.5 0.5crystal sphere ball4
0
0
4 0 0 1 1!genbox gray_plastic pedestal_top 8 8 0.5 | xform -t -4 -4 -0.5
#### 1.2 materials.mat ################################################
void plastic red_plastic
0
0
5 .7 .1 .1 .06 .1void metal steel
0
0
5 0.6 0.62 0.68 1 0void metal gold
0
0
5 0.75 0.55 0.25 0.85 0.2void plastic white_matte
0
0
5 .8 .8 .8 0 0void dielectric crystal
0
0
5 .5 .5 .5 1.5 0void plastic black_matte
0
0
5 .02 .02 .02 .00 .00void plastic gray_plastic
0
0
5 0.25 0.25 0.25 0.06 0.0#### 1.3 sky_and_ground.rad
################################################
void colorpict hdr_image
7 red green blue 140621_1530.hdr angmap.cal u v
0
0hdr_image glow sky_glow
0
0
4 1 1 1 0sky_glow source HDR_sky
0
0
4 0 0 1 180# ground
void glow ground_glow
0
0
4 1 1 1 0ground_glow source ground
0
0
4 0 0 -1 180#### 1.4 angmap.cal ################################################
{
angmap.calConvert from directions in the world (Dx, Dy, Dz) into (u,v)
coordinates on the light probe image+z is up (toward top of sphere, i.e. the zenith)
+y is North
}d = sqrt(Dx*Dx + Dy*Dy);
r = acos(Dz)/PI;
u = 0.5 - Dx/d * r;
v = 0.5 + Dy/d * r;#### 1.5 view.vf ################################################
# looking towards east
#rvu -vtv -vp -12 0 0.5 -vd 1 0 0 -vu 0 0 1 -vh 60 -vv 40
# looking towards west
#rvu -vtv -vp 12 0 0.5 -vd -1 0 0 -vu 0 0 1 -vh 60 -vv 40
# looking towards north
rvu -vtv -vp 0 -12 0.5 -vd 0 1 0 -vu 0 0 1 -vh 60 -vv 40
# looking towards south
#rvu -vtv -vp 0 12 0.5 -vd 0 -1 0 -vu 0 0 1 -vh 60 -vv 40#### 1.6 cmd.sh ################################################
oconv ./materials.mat ./sky_and_ground.rad ./geom.rad > ./scene.octrvu -vf ./view.vf ./scene.oct
#ximage ./sky.hdr
rpict -x 2400 -y 2400 -t 30 -ab 1 -ar 50000 -aa 0.08 -ad 128 -as 64 -st 0
-lw 0 -lr 8 -vf ./view.vf ./scene.oct > ./image.hdrpfilt -1 -x /3 -y /3 -r 1 ./image.hdr > ./image_filtered.hdr
Step2. put the 140621_1530.hdr file provided by LBNL (
http://flexskycam.lbl.gov) in the same folderStep3. run the cmd.sh batch file to produce the rendering
On Sat, Jun 28, 2014 at 7:28 AM, Andrew McNeil <[email protected]> wrote:
Hi All,
I haven't done any testing myself, I wanted to make the data available
right away so that others could tinker too (and maybe make it easier for
me).Joe - You're correct that the HDR sky image essentially replaces the
skyfunc modifier, here's a thread where Kyle was doing the same thing:
http://www.radiance-online.org/pipermail/radiance-general/2012-October/008962.htmlRob - In a clear sky condition our HDR images won't capture the full
luminance of the sun. Mksource would be helpful to zero out the pixels, but
the source that it makes won't be useful without adjusting the radiance of
the source to match that of the sun.Best,
AndyOn Fri, Jun 27, 2014 at 2:58 PM, Rob Guglielmetti < >>>> [email protected]> wrote:
Hi German, and everyone else. Certainly one could use these HDR images
to generate sky vectors and apply them to daylight coefficients for a given
model(s). Greg Ward has created a cool tool called mksource to facilitate
this process in Radiance, identifying small, intense pixels in the image;
creating and placing Radiance light sources in their stead, and zeroing the
pixels to avoid double counting.Considerations:
- Capturing the true (full) dynamic range of an exterior scene with
direct sun is difficult.
- Using locally-captured HDR images for daylight availability analysis
is statistically dubious. Granted, so is using TMY data, for different
reasons. This is why I changed the title of this list to "considerations",
from "problems". =)On Fri, Jun 27, 2014 at 3:38 PM, CHI-German Molina <[email protected]> >>>>> wrote:
Wow, I have been thinking on doing this for a while... although I have
no idea where to start from.Is it possible to calculate the Daylight Coefficients of the building;
and use the HDR image to generate sky vectors and calculate different
options for optimizing daylighting?I am picturing a computer that, every 5 minutes, calculate the sky
vector, computes the interior lighting conditions, and simulates the
different lighting options performing a whole-building lighting control
with no photo sensors. Even more, maybe a whole neighborhood could use the
same camera. Nonsense?Thanks for sharing!
2014-06-27 0:59 GMT-04:00 Joe Smith <[email protected]>:
Hi, Andy, thanks for sharing LBNL's sky mapping experiment!
Can you kindly advice on resources that elaborate on how to use HDR
sky image for daylight simulation? Does it involve specifying the HDR
image, rather than a "skyfunc", as the material identifier for the sky
geometry? How is the pixel value of a given point on the HDR image
converted to luminance value of the corresponding position on the sky?Thanks!
- JoeAndrew McNeil <[email protected]>?2014?6?27???
Hi Everyone,
LBNL has installed an HDR sky camera at our new FLEXLAB site:
http://flexskycam.lbl.gov. I've uploaded sample data, including hdr
images and csv datafiles, recorded by the camera for three days over the
past week( clear, partly cloudy and overcast). We're happy to share more
data with other researchers and daylight practitioners (but we don't have
much to offer yet).The images can be mapped to a Radiance sky for simulation under real
sky conditions. I have not used the sky HDR images yet, myself, so if
anybody uses them successfully please report back and share what you've
done!Questions about the camera hardware and capabilities should be
directed to Chris Humann at Terrestrial Light.Best,
Andy_______________________________________________
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