## Chapter 11

## Global Illumination

“If it looks like computer graphics, it is not good computer graphics.”

—Jeremy Birn

Radiance is the final quantity computed by the rendering process. So far, we have been using the reflectance equation to compute it:

(11.1)

$$\begin{array}{c}\hfill {L}_{o}(\mathbf{p},\mathbf{v})={\int}_{\mathbf{l}\in \mathrm{\Omega}}f(\mathbf{l},\mathbf{v}){L}_{i}(\mathbf{p},\mathbf{l}){(\mathbf{n}\xb7\mathbf{l})}^{+}d\mathbf{l},\end{array}$$where ${L}_{o}(\mathbf{p},\mathbf{v})$ is the outgoing radiance from the surface location $\mathbf{p}$ in the view direction $\mathbf{v}$ , $\mathrm{\Omega}$ is the hemisphere of directions above $\mathbf{p}$ , $f(\mathbf{l},\mathbf{v})$ is the BRDF evaluated for $\mathbf{v}$ and the current incoming direction $\mathbf{l}$ , ${L}_{i}(\mathbf{p},\mathbf{l})$ is the incoming radiance into $\mathbf{p}$ from $\mathbf{l}$ , and ${(\mathbf{n}\xb7\mathbf{l})}^{+}$ is the dot product between $\mathbf{l}$ and ...

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