Editing Cornell box (section)

== History  ==
=== The Original Cornell Box ===
The original Cornell Box was described by Cindy M. Goral, Kenneth E. Torrance, and Donald P. Greenberg in their 1984 paper titled ''Modeling the Interaction of Light Between Diffuse Surfaces'', presented at SIGGRAPH '84.<ref name="CornellBox1984"/>

In this initial version, the interior was painted in red, blue, and gray, and no occluding objects were placed inside the box. Rather than placing a light source inside, the box was illuminated indirectly using a set of lights and a white diffuse surface.<br>
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Cornell_box_render_SIGGRAPH'84.png | The rendered image is on the left, and photo reference on the right.<br>The ray tracing program was written in [[C (programming language)|C]] on a [[VAX-11/780]] [[superminicomputer]].
Cornell_box_setup_1984.png | Sketch of the scene configuration from the same paper with Cornell box referred to as a '''test cube'''.
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=== Hemi-Cube Form Factors ===
This simulation of the Cornell Box was carried out by [[Michael F. Cohen]] and Donald P. Greenberg for their 1985 paper ''The Hemi-Cube: A Radiosity Solution for Complex Environments'' presented at SIGGRAPH '85.<ref name="HemiCube">Michael F. Cohen, Donald P. Greenberg. ''[https://dl.acm.org/doi/10.1145/325165.325171 The Hemi-Cube: A Radiosity Solution for Complex Environments]''. SIGGRAPH 1985, Vol. 19, No. 3, pp. 31-40.</ref> The hemi-cube technique allowed [[Form factor (radiative transfer)|form factors]] to be calculated using scan conversion algorithms, which were supported by hardware at the time, and made it possible to calculate shadows from occluding objects inside the scene.

This version of the Cornell Box was the first to feature objects placed inside — a short block on the left side, a tall block on the right side, and a light source in the center of the 'ceiling'. This configuration matches the scene data<ref name="CornellBoxData"/> shared by Cornell University discussed in [[Cornell box#Scene data|Scene data (section)]]. This layout became a standard reference and was widely reproduced, but in many rendered versions of this scene, the arrangement of the blocks is often mirrored.
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=== Spherical Harmonics ===
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| [[File:Cornell_box_1991_measured.jpg|320px]]
| Photographic image reference<ref name="CornellBoxWebsiteComparisonSubpage">[https://www.graphics.cornell.edu/online/box/compare.html Cornell Box Comparison subpage]</ref>
| [[File:Cornell_box_1991_simulated.jpg|320px]]
| Synthetic rendered image<ref name="CornellBoxWebsiteComparisonSubpage"/>
}}</div>{{stack end}}
François X. Sillion, James Arvo, Stephen Westin, and Donald P. Greenberg made significant contributions to global illumination in computer graphics, particularly through the use of [[spherical harmonics]].

In their 1991 paper presented at SIGGRAPH '91, ''A Global Illumination Solution for General Reflectance Distributions'',<ref name="SphericalHarmonics">{{Cite journal|last=Sillion|first=François X.|date=1991|title=A Global Illumination Solution for General Reflectance Distributions|journal=SIGGRAPH '91 Conference Proceedings|pages=187–196|publisher=ACM|location=Las Vegas, United States|url=https://inria.hal.science/inria-00510145/document?}}</ref> they demonstrated a method that extended light transfer simulations to handle complex reflectance properties beyond ideal diffuse or specular surfaces. This approach utilized spherical harmonic decomposition to encode [[bidirectional reflectance distribution function]]s (BRDFs) and directional intensity distributions, allowing for more accurate and efficient rendering of materials with complex reflectance characteristics. In this version of the Cornell box, the blocks are arranged in a flipped configuration, and the tall block features a mirror-like (aluminum) surface instead of a diffuse one.<ref name="SphericalHarmonics"/> This modification does not align with the scene data<ref name="CornellBoxData"/> shared by Cornell University and could contribute to the misconception described in [[Cornell box#Scene data|Scene data (section)]].

The photographic and synthetic image references found in the SIGGRAPH '91 paper,<ref name="SphericalHarmonics"/> in a specific subpage of the Cornell University website named 'Cornell Box Comparison'<ref name="CornellBoxWebsiteComparisonSubpage"/> and in the officially provided reproducible data<ref name="CornellBoxData"/> are all unique, even though they look fairly identical. Common misconceptions are discussed in the section below, but it is worth noting that while the synthetic image found in this section is entirely different from the 'officially' provided synthetic reference,<ref name="CornellBoxData"/> the photographic reference closely resembles the 'official' photographic image discussed in [[Cornell box#Photographic Images|Photographic Images (section)]]. At first glance, it is easy to notice the changed camera position, as well as the addition of a square object obstructing and absorbing light — a so-called '[[Flag (lighting)|flag]]', often used in photography to achieve the opposite effect of '[[Reflector (photography)#Board reflectors|bounce cards]]'. It was likely used to block distracting effects caused by the strong light source being directly visible by the camera. This absorbing object is not present in the officially provided [[Cornell box#Photographic Images|photographic image (section)]].