View Factor - View Factors of Differential Areas

View Factors of Differential Areas

Taking the limit of a small flat surface gives differential areas, the view factor of two differential areas of areas and at a distance S is given by:

F_{1 \rarr 2} = \frac{\cos\theta_1 \cos\theta_2}{\pi S^2}\hbox{d}A_2

where and are the angle between the surface normals and a ray between the two differential areas.

The view factor from a general surface to another general surface is given by:

F_{1 \rarr 2} = \frac{1}{A_1} \int_{A_1} \int_{A_2} \frac{\cos\theta_1 \cos\theta_2}{\pi S^2}\, \hbox{d}A_2\, \hbox{d}A_1


The view factor is related to the etendue.

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