Theory, Analysis and Applications of 2D Global Illumination

1Disney Research Zürich 2UC San Diego 3Limbic Software 4RWTH Aachen University

In ACM Transactions on Graphics (Presented at SIGGRAPH), 2012

Visualization of flux, irradiance and radiance in the standard 3D settings (a-c), and the simplified 2D setting (d-f).


We investigate global illumination in 2D and show how this simplified problem domain leads to practical insights for 3D rendering.

We first derive a full theory of 2D light transport by introducing 2D analogues to radiometric quantities such as flux and radiance, and deriving a 2D rendering equation. We use our theory to show how to implement algorithms such as Monte Carlo ray tracing, path tracing, irradiance caching, and photon mapping in 2D, and demonstrate that these algorithms can be analyzed more easily in this domain while still providing insights for 3D rendering.

We apply our theory to develop several practical improvements to the irradiance caching algorithm. We perform a full second-order analysis of diffuse indirect illumination, first in 2D, and then in 3D by deriving the irradiance Hessian, and show how this leads to increased accuracy and performance for irradiance caching. We propose second-order Taylor expansion from cache points, which results in more accurate irradiance reconstruction. We also introduce a novel error metric to guide cache point placement by analyzing the error produced by irradiance caching. Our error metric naturally supports anisotropic reconstruction and, in our preliminary study, resulted in an order of magnitude less error than the "split-sphere" heuristic when using the same number of cache points.



Wojciech Jarosz, Volker Schönefeld, Leif Kobbelt, Henrik Wann Jensen. Theory, Analysis and Applications of 2D Global Illumination. ACM Transactions on Graphics (Presented at SIGGRAPH), 31(5):125:1–125:21, September 2012.
    author = "Jarosz, Wojciech and Schönefeld, Volker and Kobbelt, Leif and Jensen, Henrik Wann",
    title = "Theory, Analysis and Applications of 2D Global Illumination",
    journal = "ACM Transactions on Graphics (Presented at SIGGRAPH)",
    volume = "31",
    number = "5",
    month = "sep",
    year = "2012",
    pages = "125:1–125:21",
    doi = "10.1145/2231816.2231823"
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