<p>Attached is page 34 of "Advanced Global Illumination", 2nd edition, by Dutre et al. I don't understand how (2.22) is derived from (2.21) and the given incident radiance distribution <span class="math-container">$L(x\leftarrow\Psi)=L_{in}\delta(\Psi-\Theta)$</span>. Could you please give me a detailed derivation? Thanks a lot!</p>

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Ask for detailed derivation of a formula in "Advanced Global Illumination"
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# Ask for detailed derivation of a formula in "Advanced Global Illumination"

(Asked by: username_0 on 2018-11-10)

Attached is page 34 of "Advanced Global Illumination", 2nd edition, by Dutre et al. I don't understand how (2.22) is derived from (2.21) and the given incident radiance distribution $L(x\leftarrow\Psi)=L\_{in}\delta(\Psi-\Theta)$. Could you please give me a detailed derivation? Thanks a lot!

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