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Measurement of illumination 

Illumination distribution on the atrium floor.

Presentation of illuminance values measured with a Lux-Meter on the floor of the Atrium under identical lighting conditions as the software evaluation.

Table of measured illuminance at sampled points on the floor of the atrium.
 

9.0  50  50  54  50  50  67  62  62  69  64  67  57  66
7.40  51  48  69  53  90  55 165  62 187  66 182  57 139
6.00  96 125 164 118 125 141 234 260 301 305 262 210 183
4.52   - 116 151 118  90 121 230   -   -   -   -   - 171
3.00 102 121   - 124 106 141 247 269 300 318 269 213 181
1.60 124  53  56  63 112  61 194  66 198  65 178  63 134
0.00  56  48  50  60  63  57  66  61  71  61  68  58  63
0.00 3.58 7.17 10.75 14.34 17.92 21.51 25.09 28.68 32.26 35.85 39.43  46.60
 
Red numbers are distances in meter in the x and z coordinates.


 



Computer generated illuminance values

Four methods are represented, the first one is rendering using BRDF measured attribute surfaces. The second uses diffuse Kd and specular Ks reflectance coefficients averaged from the corresponding BRDF values for a given material. The third method is similar to the second one. This time only averaged diffuse reflectance is considered, and we dub this approach "radiosity".  In the last method, surface attributes were evaluated by visual observation of the materials. We refer to the fourth method as an "artistic approach". For all methods 84 sample points were considered. The simulation results were obtained using the Density Estimation Particle Tracing (DEPT) global illumination algorithm described in [1] which is a part of the Inspirer (Integra, Inc.) system.
 

Summary of comparative data analyses:


[1] V.Volevich,K.Myszkowski, A.Khodulev, and Kopylov E.A. Using the Visible Differences Predictor to improve performance in progressive global illumination computations. ACM Transactions on Graphics,  Vol. 19, No. 2, pp. 122-161, 2000.
 



Graphical comparison of simulation results

Illumination data for z = 9.00

Illumination data for z = 7.40
Illumination data for z = 6.00
Illumination data for z = 4.52
Illumination data for z = 3.00
Illumination data for z = 1.60
Illumination data for z = 0.00
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