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Natural Light in DesignNatural Light in DesignUsing simulation tools to explore realistic daylight-responsive solutionsUsing simulation tools to explore realistic daylight-responsive solutions
Christoph Reinhart, Ph.D.Christoph Reinhart, Ph.D.Overview - RadianceOverview - Radiance
Daylight Factor Visual Comfort
Daylight Autonomy Avoidance of Direct Sunlight
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Overview - Radiance
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Objectives for this module
• Export to Radiance
• Radiance Algorithm
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Advanced Radiance Visualizations IV
simulation: NRC
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Some Facts on Radiance
Physically based backward raytracer – no fudge factors.
A wide variety of material properties and sky models.
Longish learning curve.
“Magic” lies in simulation parameters.
2004 Survey: >180 participants, 40 different tools, >50% of picks for Radiance based tools.
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Backward vs. Forward Raytracing
forward raytracer backward raytracer (Radiance)
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Light. Res. & Technology Mardaljevic, 1995
Radiance Validation Studies I
Validation Radiance/ sky scanner data for a clear glazing with/without a lightshelf (Radiance materials: “plastic”, “metal”, “glass”)
Figure by MIT OCW.
102
103
Illum
inat
ion
(lux)
RE
(%)
104
105102_92_13h00 121_92_14h15
10
100
1000
-200 2
Distance from window (m) Distance from window (m)4 6 8 10
0
20
-200 2 4 6 8 10
0
20
Prediction
Measurement
Clear Glazing Clear Glazing
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Parameter Study Radiance: ab 0 to ab 8
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(1) define a camera view
(2) Ecotect lighting simulation
(3) Export to Radiance
(4) Visualization (ab 1 & sunny)
Ecotect Demo – Export to Radiance
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Export to Radiance Menu
Radiance Export
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Export to Radiance MenuRadiance Control Panel
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# Sky definition.
!gensky 4 1 12.76 -c -a 45.500 -o -73.700 -m -75.000 -B 40.307263
skyfunc glow sky_mat
0 0 4 1 1 1 0
sky_mat source sky
0 0 4 0 0 1 180
skyfunc glow ground_glow
0 0 4 1 .8 .5 0
ground_glow source ground
0 0 4 0 0 -1 180
sky.rad
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Gensky (sky description in Radiance)Under Google type: Radiance – gensky
-s Sunny sky without sun. The sky distribution will correspond to a standard CIE clear day.
+s Sunny sky with sun. In addition to the sky distribution function, a source description of the sun is generated.
-c Cloudy sky. The sky distribution will correspond to a standard CIE overcast day.
-i Intermediate sky without sun. The sky will correspond to a standard CIE intermediate day.
+i Intermediate sky with sun. In addition to the sky distribution, a (somewhat subdued) sun is generated.
-u Uniform cloudy sky. The sky distribution will be completely uniform
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interior view exterior view
Visualization – internal vs. external
indirect 0detail mediumvariability mediumquality medium
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ab 0 ab 1
Visualization – ab 0,1,2,3,
ab 3ab 2
detail medium - variability medium - quality medium
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ab 5
Detail: low
Variability: low
Quality: low
Image Parameters
ab 5
Detail: high
Variability: low
Quality: low
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ab 5
Detail: low
Variability: low
Quality: low
Image Parameters
ab 5
Detail: low
Variability: high
Quality: low
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ab 5
Detail: low
Variability: low
Quality: low
Image Parameters
ab 5
Detail: low
Variability: low
Quality: high
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ab 5
Detail: low
Variability: low
Quality: low
Image Parameters
ab 5
Detail: high
Variability: high
Quality: high
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Limitations of Radiance
Radiance will not necessarily `find` the sun.