Modified Three phase Odd radiation levels


#1

Hello All,

The simplistic test script below generates radiation levels for a single day for a Northern latitude and a Southern latitude. The southern latitude has an odd ball value in row 13 well outside the expected values compared to the same steps used in the northern latitude example.

Note: the script is for a single flat panel facing up and a single sensor point. (-n 6 in the rfluxmtx command is for 6 cores).

Any suggestions would be appreciated.

Regards
Terrance McMinn

#!/bin/bash

cat > “AUS_WA_Swanbourne.946140_52_SW_CZ0506_RMY2012A-m.epw” << EOF
LOCATION,Swanbourne,WA,AUS,NatHERS-TMY2-A BoM 9215 CZ0506,946140,-31.960,115.760,8.0,41.0
DESIGN CONDITIONS,1,2017 ASHRAE Handbook – Fundamentals - Chapter 14 Climatic Design Information,Heating,7,6.4,7.5,1,4.1,17,2.3,4.5,15,17.3,16.4,15.2,16.4,3.9,80,Cooling,2,10.2,35.2,20.1,32.9,19.9,30.9,19.6,23.3,28.8,22.3,27.6,21.6,26.8,4.9,60,21.7,16.5,25.6,20.7,15.5,24.3,20,14.8,24,69.3,28.5,65.5,27.7,63,26.5,27.7,Extremes,12.8,11,9.6,4.3,39.8,0.9,1.7,3.7,41.1,3.1,42.1,2.6,43.1,2,44.3,3.6
TYPICAL/EXTREME PERIODS,6,Summer - Week Nearest Max Temperature For Period,Extreme,3/ 5,3/11,Summer - Week Nearest Average Temperature For Period,Typical,2/ 5,2/11,Winter - Week Nearest Min Temperature For Period,Extreme,8/12,8/18,Winter - Week Nearest Average Temperature For Period,Typical,7/ 8,7/14,Autumn - Week Nearest Average Temperature For Period,Typical,5/27,6/ 2,Spring - Week Nearest Average Temperature For Period,Typical,11/12,11/18
GROUND TEMPERATURES,3,.5,18.75,20.80,22.08,22.50,21.82,20.17,18.09,16.01,14.60,14.22,14.96,16.59,2,17.89,19.51,20.71,21.27,21.28,20.35,18.92,17.29,15.96,15.31,15.47,16.40,4,17.56,18.66,19.59,20.12,20.46,20.06,19.22,18.12,17.09,16.43,16.27,16.68
HOLIDAYS/DAYLIGHT SAVINGS,No,0,0,0
COMMENTS 1,“Reference Meteorological Years 2012 developed for the Australian National House Energy Rating Scheme (NatHERS) 2012; three series: A, B, and C denoting months selected based on 50% (A), 33% (B) or 17% © solar radiation weights; TMY2 months selected from 1967-2012 out of 45 years of data; The data files are publicly-funded data provided by the Australian Commonwealth and no person or entity may charge for its supply or use. While the Commonwealth has exercised reasonable care and skill in the preparation and collation of the data files, the data is supplied on an as is basis, without warranty of any kind. The Commonwealth accepts no liability for any direct, indirect, special or consequential damages, loss, damage or cost arising from and relating to, any use of the data and/or the information associated with it.”
COMMENTS 2,“Downloaded from Climate.OneBuilding.Org – Ground temps represent undisturbed earth temperatures - calculated from this weather data.”
DATA PERIODS,1,1,TMY2 Year,Sunday,1/ 1,12/31
2000,3,22,1,60,A7A7A7A7?0?5?5?5I44I6I5A7A7A7A700A7?00,14.0,11.5,85,102100,0,1371,340,0,0,0,0,0,0,0,157,5.1,6,5,777.7,77777,9,999999999,20,0.0000,99,88,0.100,0.0,1.0
2000,3,22,2,60,A7E8E8E8?0?5?5?5I4
4I6I5A7A7A7A700E8*
?00,13.1,10.2,83,102100,0,1371,334,0,0,0,0,0,0,0,135,4.1,6,5,777.7,77777,9,999999999,19,0.0000,99,88,0.100,0.0,1.0
2000,3,22,3,60,A7E8E8E8?0?5?5?5I4
4I6I5A7A7A7A700E8*?00,12.8,9.9,82,102200,0,1371,329,0,0,0,0,0,0,0,157,5.1,6,5,777.7,77777,9,999999999,18,0.0000,99,88,0.100,0.0,1.0
2000,3,22,4,60,A7A7A7A7?0?3?3?3I4
4I6I5A7A7A7A700A7*
?00,12.4,8.8,79,102100,0,1371,327,0,0,0,0,0,0,0,157,4.6,5,5,777.7,77777,9,999999999,17,0.0000,99,88,0.100,0.0,1.0
2000,3,22,5,60,A7E8E8E8?0?3?3?3I4
4I6I5A7A7A7A700E8*?00,12.1,8.9,81,102300,0,1371,324,0,0,0,0,0,0,0,157,5.1,5,5,777.7,77777,9,999999999,17,0.0000,99,88,0.100,0.0,1.0
2000,3,22,6,60,A7E8E8E8?0?3?3?3I4
4I6I5A7A7A7A700E8*
?00,11.3,9.1,86,102300,0,1371,323,0,0,0,0,0,0,0,157,4.1,3,5,777.7,77777,9,999999999,17,0.0000,99,88,0.100,0.0,1.0
2000,3,22,7,60,A7A7A7A7?0?3?3?3I4
4I6I5A7A7A7A700A7*?00,11.3,9.5,89,102400,108,1370,319,55,381,25,5689,17953,3910,43,157,3.6,2,5,777.7,77777,9,999999999,18,0.0000,99,88,0.100,0.0,1.0
2000,3,22,8,60,A7E8E8E8?0A3A3D3I4
4I6I5A7A7A7A700E8*
?00,13.7,9.9,78,102400,403,1370,320,265,742,46,28519,67440,7375,96,157,5.1,1,5,777.7,77777,9,999999999,18,0.0000,99,88,0.100,0.0,1.0
2000,3,22,9,60,A7E8E8E8?0A3A3D3I4
4I6I5A7A7A7A700E8*?00,15.8,9.9,68,102400,670,1370,331,489,873,61,53046,87436,9142,145,135,5.7,1,5,777.7,77777,9,999999999,18,0.0000,99,88,0.100,0.0,1.0
2000,3,22,10,60,A7A7A7A7?0A3A3D3I4
4I6I5A7A7A7A700A7*
?00,18.5,9.9,57,102400,891,1370,341,681,934,72,73636,95648,10332,192,112,6.7,0,5,777.7,77777,9,999999999,18,0.0000,99,88,0.100,0.0,1.0
2000,3,22,11,60,A7E8E8E8?0A3A3D3I4
4I6I5A7A7A7A700E8*?00,19.9,9.7,52,102300,1050,1370,354,799,913,97,85603,93950,13304,280,135,6.7,0,5,777.7,77777,9,999999999,18,0.0000,99,88,0.100,0.0,1.0
2000,3,22,12,60,A7E8E8E8?0A3A3D3I4
4I6I5A7A7A7A700E8*
?00,21.2,8.7,45,102300,1138,1370,360,895,962,94,95736,99053,12701,331,112,7.2,0,5,777.7,77777,9,999999999,17,0.0000,99,88,0.100,0.0,1.0
2000,3,22,13,60,A7A7A7A7?0A3A3D3I4
4I6I5A7A7A7A700A7*?00,22.1,8.7,42,102200,1146,1370,366,904,971,90,96815,100024,12171,330,112,7.2,0,5,777.7,77777,9,999999999,16,0.0000,99,88,0.100,0.0,1.0
2000,3,22,14,60,A7E8E8E8?0A3A3D3I4
4I6I5A7A7A7A700E8*
?00,23.3,8.2,38,102100,1077,1370,370,841,966,80,90324,99335,11037,264,135,6.7,0,5,777.7,77777,9,999999999,16,0.0000,99,88,0.100,0.0,1.0
2000,3,22,15,60,A7E8E8E8?0A3A3D3I4
4I6I5A7A7A7A700E8*?00,23.9,8.6,38,102000,933,1370,376,712,942,69,76878,96485,9852,196,112,5.7,0,5,777.7,77777,9,999999999,16,0.0000,99,88,0.100,0.0,1.0
2000,3,22,16,60,A7A7A7A7?0A3A3D3I4
4I6I5A7A7A7A700A7*
?00,23.9,7.8,36,102000,724,1370,379,514,857,61,55544,86164,9065,152,112,5.7,1,5,777.7,77777,9,999999999,15,0.0000,99,88,0.100,0.0,1.0
2000,3,22,17,60,A7E8E8E8?0A3A3D3I4
4I6I5A7A7A7A700E8*?00,23.1,8.0,38,102000,466,1370,378,305,771,43,33147,73066,6728,105,112,6.2,1,5,777.7,77777,9,999999999,16,0.0000,99,88,0.100,0.0,1.0
2000,3,22,18,60,A7E8E8E8?0A3A3D3I4
4I6I5A7A7A7A700E8*
?00,21.7,8.2,42,102100,175,1370,374,99,540,30,10136,36969,4912,53,112,5.7,1,5,777.7,77777,9,999999999,16,0.0000,99,88,0.100,0.0,1.0
2000,3,22,19,60,A7A7A7A7?0A3A3D3I4
4I6I5A7A7A7A700A7*?00,19.9,8.8,49,102000,0,1370,368,0,0,0,0,0,0,0,112,3.6,1,5,777.7,77777,9,999999999,17,0.0000,99,88,0.100,0.0,1.0
2000,3,22,20,60,A7E8E8E8?0?3?3?3I4
4I6I5A7A7A7A700E8*
?00,18.1,9.3,56,102100,0,1370,359,0,0,0,0,0,0,0,112,3.1,1,5,777.7,77777,9,999999999,17,0.0000,99,88,0.100,0.0,1.0
2000,3,22,21,60,A7E8E8E8?0?3?3?3I4
4I6I5A7A7A7A700E8*?00,17.6,9.1,57,102200,0,1370,351,0,0,0,0,0,0,0,112,3.6,1,5,777.7,77777,9,999999999,17,0.0000,99,88,0.100,0.0,1.0
2000,3,22,22,60,A7A7A7A7?0?3?3?3I4
4I6I5A7A7A7A700A7*
?00,17.9,9.7,59,102200,0,1370,349,0,0,0,0,0,0,0,90,4.1,1,5,777.7,77777,9,999999999,18,0.0000,99,88,0.100,0.0,1.0
2000,3,22,23,60,A7E8E8E8?0?3?3?3I4
4I6I5A7A7A7A700E8*?00,17.2,9.7,61,102200,0,1370,351,0,0,0,0,0,0,0,112,3.6,1,5,777.7,77777,9,999999999,18,0.0000,99,88,0.100,0.0,1.0
2000,3,22,24,60,A7E8E8E8?0?5?5?5I4
4I6I5A7A7A7A700E8*
?0*0,16.7,9.7,63,102100,0,1370,347,0,0,0,0,0,0,0,112,4.6,1,5,777.7,77777,9,999999999,18,0.0000,99,88,0.100,0.0,1.0

EOF

cat > “material.mat” << EOF
void plastic Default_Material
0
0
5 0.4 0.4 0.4 0 0
EOF

cat > “roof.rad” << EOF
Default_Material polygon square
0
0
12
-0.5 -0.5 0
0.5 -0.5 0
0.5 0.5 0
-0.5 0.5 0
EOF

cat > “sensors.pts” << EOF
0 0 0 0 0 1
EOF

cat > “sky_white.sky” << EOF
#@rfluxmtx h=u u=Z
void glow groundglow
0
0
4
1 1 1 0

groundglow source ground
0
0
4
0 0 -1 180

#@rfluxmtx h=r4 u=Z
void glow skyglow
0
0
4
1 1 1 0

skyglow source sky
0
0
4
0 0 1 180
EOF

epw2wea AUS_WA_Swanbourne.946140_52_SW_CZ0506_RMY2012A-m.epw AUS_WA_Swanbourne.946140_52_SW_CZ0506_RMY2012A-m.wea
gendaymtx -m 4 -O1 AUS_WA_Swanbourne.946140_52_SW_CZ0506_RMY2012A-m.wea > matrix.smx
rfluxmtx -v -n 6 -I+ -ab 12 -ad 10000 -lw 1e-4 -w- < sensors.pts - sky_white.sky material.mat roof.rad > photocells.vmx
dctimestep photocells.vmx matrix.smx > res.dat
rmtxop -fa -c 1 1 1 res.dat | rmtxop -t - | getinfo - > radiation.tab

cat > “TWN_Taipei.466960_IWEC-m.epw” << EOF
LOCATION,TAIPEI,-,TWN,IWEC Data,466960,25.07,121.55,8.0,6.0
DESIGN CONDITIONS,1,Climate Design Data 2009 ASHRAE Handbook,Heating,1,9,10.4,3.8,5,11.4,5.3,5.5,11.9,9,17.3,8.2,17.5,1.8,90,Cooling,7,7.2,34.9,26.8,34,26.9,33.2,26.7,28,32.7,27.6,32,27.2,31.4,5,270,27,22.7,30.5,26.2,21.7,29.9,26.1,21.5,29.8,89.8,32.9,88,32.5,86.4,31.6,833,Extremes,8.8,7.8,7.1,34,6.4,36.7,2,1.5,4.9,37.8,3.8,38.6,2.7,39.5,1.2,40.5
TYPICAL/EXTREME PERIODS,6,Summer - Week Nearest Max Temperature For Period,Extreme,7/20,7/26,Summer - Week Nearest Average Temperature For Period,Typical,6/15,6/21,Winter - Week Nearest Min Temperature For Period,Extreme,1/27,2/ 2,Winter - Week Nearest Average Temperature For Period,Typical,12/22,1/ 5,Autumn - Week Nearest Average Temperature For Period,Typical,10/13,10/19,Spring - Week Nearest Average Temperature For Period,Typical,4/ 5,4/11
GROUND TEMPERATURES,3,.5,17.22,16.68,17.64,19.15,23.10,26.14,28.19,28.82,27.75,25.39,22.23,19.30,2,19.22,18.25,18.45,19.25,21.89,24.28,26.19,27.21,26.99,25.65,23.48,21.17,4,20.88,19.88,19.67,19.97,21.46,23.07,24.54,25.57,25.81,25.23,23.95,22.39
HOLIDAYS/DAYLIGHT SAVINGS,No,0,0,0
COMMENTS 1,“IWEC- WMO#466960 - Asia – Original Source Data © 2001 American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), Inc., Atlanta, GA, USA. www.ashrae.org All rights reserved as noted in the License Agreement and Additional Conditions. DISCLAIMER OF WARRANTIES: The data is provided ‘as is’ without warranty of any kind, either expressed or implied. The entire risk as to the quality and performance of the data is with you. In no event will ASHRAE or its contractors be liable to you for any damages, including without limitation any lost profits, lost savings, or other incidental or consequential damages arising out of the use or inability to use this data.”
COMMENTS 2, – Ground temps produced with a standard soil diffusivity of 2.3225760E-03 {m**2/day}
DATA PERIODS,1,1,Data,Sunday, 1/ 1,12/31
1993,3,22,1,60,A7A7E8B80?9?9?9?9?9?9?9A7A7B8B8A7A70E800,17.0,17.0,100,102100,0,1377,362,0,0,0,0,0,0,0,120,1.0,8,7,3.5,22000,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,2,60,A7A7E8E80?9?9?9?9?9?9?9A7A7A7A7A7A70E800,17.2,16.6,96,102100,0,1377,358,0,0,0,0,0,0,0,0,0.0,7,6,2.0,150,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,3,60,A7A7E8B80?9?9?9?9?9?9?9A7A7B8B8A7A70E800,17.0,17.0,100,102100,0,1377,358,0,0,0,0,0,0,0,0,0.0,8,6,1.8,150,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,4,60,A7A7E8B80?9?9?9?9?9?9?9A7A7B8B8A7A70E800,17.0,17.0,100,102100,0,1377,358,0,0,0,0,0,0,0,0,0.0,8,6,1.8,150,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,5,60,A7A7E8E80?9?9?9?9?9?9?9A7A7A7A7A7A70E800,17.0,16.1,94,102100,0,1377,357,0,0,0,0,0,0,0,240,1.0,9,6,3.0,150,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,6,60,A7A7E8B80?9?9?9?9?9?9?9A7A7B8B8A7A70E800,17.0,16.0,94,102200,0,1377,354,0,0,0,0,0,0,0,0,0.0,9,5,5.0,210,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,7,60,A7A7E8B80H9H9H9I9I9I9I9A7A7B8B8A7A70E800,17.0,16.0,94,102200,158,1377,354,18,0,18,2100,0,2100,690,0,0.0,9,5,4.5,1050,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,8,60,A7A7E8E80G9G9G9I9I9I9I9A7A7A7A7A7A70E800,18.4,16.9,91,102300,473,1377,359,115,0,115,12900,0,13000,4410,0,0.0,9,4,3.3,2400,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,9,60,B8C8E8B80H9H9H9I9I9I9I90B8B8B8B800E800,20.3,16.9,80,102200,755,1377,368,278,70,240,31200,6300,27700,7410,0,0.0,8,4,3.0,2400,9,999999999,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,10,60,B8C8E8B80H9H9H9I9I9I9I9A7A7B8B8A7A70E800,22.3,16.8,71,102200,986,1377,378,455,148,348,50500,13500,41400,10790,0,0.0,8,4,2.8,22000,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,11,60,A7A7E8E80G9G9G9I9I9I9I9A7A7A7A7A7A70E800,24.2,16.7,63,102200,1150,1377,388,610,221,425,68000,20200,50200,16580,0,0.0,7,4,2.8,2400,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,12,60,A7A7E8B80H9H9H9I9I9I9I9A7A7B8B8A7A70E800,27.0,19.0,62,102100,1235,1377,402,793,481,360,87200,43500,46900,19400,210,0.5,6,3,3.5,22000,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,13,60,A7A7E8B80H9H9H9I9I9I9I9A7A7B8B8A7A70E800,28.0,19.0,58,102000,1237,1377,404,867,608,320,96600,55100,42600,17250,330,2.5,5,2,5.0,22000,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,14,60,A7A7E8E80G9G9G9I9I9I9I9A7A7A7A7A7A70E800,25.3,19.3,69,101900,1155,1377,385,827,750,196,92500,73400,27600,8070,320,5.7,4,1,4.0,22000,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,15,60,A7A7E8B80H9H9H9I9I9I9I9A7A7B8B8A7A70E800,23.0,19.0,78,101900,995,1377,378,617,467,278,67300,41900,37700,8270,330,3.6,6,2,4.0,2100,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,16,60,A7A7E8B80H9H9H9I9I9I9I9A7A7B8B8A7A70E800,24.0,19.0,74,101900,766,1377,387,317,128,246,35400,11100,30000,6390,320,2.5,8,3,4.0,2100,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,17,60,A7A7E8E80G9G9G9I9I9I9I9A7A7A7A7A7A70E800,22.4,18.6,79,101900,486,1377,381,47,0,47,5700,0,5700,2130,330,3.1,10,4,5.0,2100,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,18,60,A7A7E8B80H9H9H9I9I9I9I9A7A7B8B8A7A70E800,21.0,18.0,83,102000,173,1377,376,13,0,13,1500,0,1500,520,290,3.0,10,5,4.0,750,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,19,60,A7A7E8B80H9H9H9I9I9I9I9A7A7B8B8A7A70E800,20.0,18.0,88,102000,0,1377,371,0,0,0,0,0,0,0,340,1.5,9,5,4.0,360,0,999999919,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,20,60,A7A7E8E80?9?9?9?9?9?9?9A7A7A7A7A7A70E800,20.0,18.5,91,102000,0,1377,375,0,0,0,0,0,0,0,310,1.5,9,6,4.5,1500,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,21,60,A7A7E8B80?9?9?9?9?9?9?9A7A7B8B8A7A70E800,20.0,18.0,88,102000,0,1377,374,0,0,0,0,0,0,0,20,1.0,9,6,4.0,900,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,22,60,A7A7E8B80?9?9?9?9?9?9?9A7A7B8B8A7A70E800,19.0,18.0,94,102000,0,1377,369,0,0,0,0,0,0,0,0,0.0,9,6,3.0,750,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,23,60,A7C8E8E80?9?9?9?9?9?9?9A7A7A7A7A7A70E800,12.9,12.9,100,102100,0,1377,334,0,0,0,0,0,0,0,0,0.0,9,6,2.0,210,0,999999099,0,0.2810,0,88,0.000,0.0,0.0
1993,3,22,24,60,A7A7E8B80?9?9?9?9?9?9?9A7A7B8B8A7A70E800,19.0,18.0,94,102000,0,1377,373,0,0,0,0,0,0,0,300,1.0,9,7,2.5,1200,0,999999099,0,0.2810,0,88,0.000,0.0,0.0

EOF

epw2wea TWN_Taipei.466960_IWEC-m.epw TWN_Taipei.466960_IWEC-m.wea
gendaymtx -m 4 -O1 TWN_Taipei.466960_IWEC-m.wea > matrix-t.smx
rfluxmtx -v -n 6 -I+ -ab 12 -ad 10000 -lw 1e-4 -w- < sensors.pts - sky_white.sky material.mat roof.rad > photocells-t.vmx
dctimestep photocells-t.vmx matrix-t.smx > res-t.dat
rmtxop -fa -c 1 1 1 res-t.dat | rmtxop -t - | getinfo - > radiation-t.tab


#2

For clarity the plots of the two sets of data using Version RADIANCE 5.2a are:



#3

Hi Terrance,

The values for up-vectors in your sky-dome are parallel to the Z axis. This might be the reason for the discrepancy.

#@rfluxmtx h=u u=Z
void glow groundglow
0
0
4
1 1 1 0

groundglow source ground
0
0
4
0 0 -1 180

#@rfluxmtx h=r4 u=Z
void glow skyglow
0
0
4
1 1 1 0

skyglow source sky
0
0
4
0 0 1 180

The value for u=Z should be changed to u=Y or u=X. I also created a very small offset between the polygon and the sensor position by moving the sensor to 0 0 0.001 0 0 1

(This is my best guess)


#4

Hello Sarith,

Thank you for your time and consideration. This seems to have solved the
problem.

  1. I should have remembered the mathematical issue of coincident points
    and moved the sensor slightly above the surface.
  2. I see I missed directed the sky dome up direction from u=Z to u=Y in
    the sky description as per your “Daylighting simulations with
    Radiance using matrix-based methods
    https://www.researchgate.net/publication/325248488_Daylighting_simulations_with_Radiance_using_matrix-based_methods?enrichId=rgreq-b3ab924bc37fa11ea23edc61feb23db6-XXX&enrichSource=Y292ZXJQYWdlOzMyNTI0ODQ4ODtBUzo2Mjc5Mjg2OTQwMTgwNDhAMTUyNjcyMTI3NTU2Nw%3D%3D&el=1_x_2&_esc=publicationCoverPdf
    work. However I am confused as to why the sky dome up vector is
    placed parallel to the ground in either the X or Y directions. It
    seems counter intuitive.

Re: Request for a change
Kind Regards
Terrance McMinn


#5

Hi Terrance,

As per my understanding, the direction for the up-vector can be any direction other than the one exactly parallel to the surface which the rays are being traced to. This convention also applies to tracing rays to the view-matrix apertures in the multi-phase methods and is implemented as such in rfluxmtx and genklemsamp. Greg will be the best person to explain the rationale for this convention (@Greg_Ward).
With regards to the tutorial, it is exactly the same as the one hosted on the Radiance website. Researchgate just appears to have better search engine indexing.

Regards,
Sarith


#6

Hello Sarith,

Thank you for your reply. You have been very helpful in what to me is a
new area of investigation.

Hopefully someone will point to the documentation on this up-vector
orientation aspect for use in the multi-phase methods. Your tutorial
shows the use but not the reasoning for selecting #@rfluxmtx u=+Y…

Re: Request for a change
Kind Regards
Terrance McMinn


#7

I think Sarith meant to say that the “up” vector can be any direction but parallel to the surface normal (i.e., perpendicular to the surface). The up vector is used to orient the azimuth of the hemisphere’s coordinate system. If the up vector is parallel to the “zenith” direction of the hemisphere you are trying to orient, then this is undefined. It is exactly the same as specifying a view up direction vector (-vu) that is parallel to the view direction (-vd) in rpict.

By convention, the up vector is defines the Y-axis orientation. The X-axis then points to the right in a right-handed coordinate system when viewed from the front side of the surface, looking down the Z-axis of the hemisphere. All coordinate systems in rfluxmtx can be specified as left-handed by prefixing their name with a minus sign (’-’). This is necessary to replicate Klems coordinate symmetry and the like.


#8

Hello Greg,

Thank you for taking the time to provide this clarification.

I assume from your description then the ‘up’ direction must not coincide
with the any surface normal used in the analysis.

A simple test case example:

genbox default simple_box 1 1 1 | xform -t -0.5 -0.5 -0.5

Sensor points at the following:

0 0 0.5 0 0 1.5
0 0 -0.5 0 0 -1.5
-0.5 0 0 -1.5 0 0
0.5 0 0 1.5 0 0
0 0.5 0 0 1.5 0
0 -0.5 0 0 -1.5 0

Then the #@rfluxmtx h=u string could not include any of the u=X, u=Y or
u=Z as at least two surface normals would be parallel to the zenith. In
this case the ‘up’ direction would need to be moved by a point (or less)
off the X, Y or Z direction to remove the parallel issue using u=ux, uy,
uz specification.

Is this interpretation correct?

Re: Request for a change
Kind Regards
Terrance McMinn


#9

I should have added a caveat, which is that the up vector is not used for the “h=u” uniform (cosine) hemisphere, so it does not matter how it is set in your case. If you were to use a hemisphere with azimuthal orientation, then you would need to adjust the up vector for your different sensor orientations.