Extracting sunlit areas from an rpict .HDR file

Hi there,

Apologies if this question may have been covered elsewhere.

I am attempting to extract the sunlit areas from a .hdr file output from rpict.

The goal is to extract the sunlit pixels in order to combine a sequence of 5 min interval images over the entire day in order to determine the pixels of the space that is sunlit and for how long
these pixels receive sunlight.

I am now using the most recent version of radiance, please ignore the old version seen in the .hdr file header below.

The sky file is

#Radiance Sky file:  

!gensky 6 21 09:00 +s -a -33.87 -o -151.21 -m -150

skyfunc glow skyglow
0 0
4 0.7 0.8 1.0 0
skyglow source sky
0 0
4 0 0 1 180

skyfunc glow grndglow
0 0
4 0.20 0.20 0.20 0
grndglow source ground
0 0
4 0 0 -1 180

The .hdr file header is

C:\VE Projects\code\daylight\1_obj_and_sky_to_oct>getinfo results/project_noWindows_plan_L02_SS_0621_0900.hdr
results/project_noWindows_plan_L02_SS_0621_0900.hdr:
        #?RADIANCE
        oconv -f "C:/VE Projects/! - code/daylight/1_obj_and_sky_to_oct/lib/project_noWindows_radiance.mtl" "C:/VE Projects/! - code/daylight/1_obj_and_sky_to_oct/lib/project_noWindows.rad"
        oconv -i octrees/project_noWindows_SS_0621_0900_temp.oct sky/SS_0621_0900.sky
        rpict -w -vtv -t 15 -vf views_grids/plan_L02.vp -x 2048 -y 2048 -ab 2 -ad 1024 -ar 64 -as 64 -ps 5 -lw 0.001
        SOFTWARE= RADIANCE 6.0a 2024-06-15 LBNL (6.0.4220c7f053)
        VIEW= -vtl -vp 15.34 13.145 97.59 -vd 0 0 -1 -vu 0 1 0 -vh 29.48 -vv 25.59 -vo 0 -va 0 -vs 0 -vl 0
        CAPDATE= 2025:07:13 21:54:32
        GMT= 2025:07:13 11:54:32
        PRIMARIES= 0.6400 0.3300 0.2900 0.6000 0.1500 0.0600 0.3333 0.3333
        FORMAT=32-bit_rle_rgbe

If there are multiple solutions to achieving this, i’d be very happy to test anything.

Thanks,
Vince

Hi Vince,

If you just want to see the sun patches, set -ab 0 -av 0 0 0 in your calculation, and only the sun patches will be non-zero in the resulting image.

Best,
-Greg

1 Like