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Figure 8: Top: A photograph <strong>of</strong> a car. Bottom: A rendered image <strong>of</strong> this<br />

car [TTOO90].<br />

color differences even more.<br />

2.2.3 Scanning the Cornell Box<br />

Because <strong>of</strong> the disadvantages mentioned in section 2.2.1, the Cornell Box setup<br />

was further enhanced. The radiometer was replaced by a scanner to verify a global<br />

illumination algorithm based on spherical harmonics [SAWG91] in 1991. Three<br />

colored filters were used to retrieve in<strong>for</strong>mation about the spectral distribution<br />

<strong>of</strong> the light. The filters transmitted a wide range <strong>of</strong> wavelengths, whereas the<br />

algorithm calculated values <strong>for</strong> three specific monochromatic channels. Thus,<br />

only visual comparisons <strong>of</strong> the structure <strong>of</strong> the illumination were possible – similar<br />

to the very first approach (see section 2.1).<br />

14

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