# What is the potential equation in PBR?

I'am studying PBR and the book introduce the potential equation. They said the potential equation can describe shooting algorithms better, and $W(x, \theta)$ describes the fraction of the radiance $L(x, \theta)$

But I could not understand the concept.

Is just $W(x, \theta)$ a fraction such as $\frac{1}{3}$(I know the original equation is quite complicate, integral) to reduce the radiance $L$ which is derived from a light source? (because the L would be diminished if it collides with objects).

• Can you give a chapter or page number where $W(x,\theta)$ is described in PBR? – user81327 Jun 20 '17 at 13:34
• I'am using a book 'Advanced Global Illumination 2ed' (page 89 chapter 4.2) and referring to "dspace5.zcu.cz/bitstream/11025/15417/1/Willems_94.pdf" (page 4, 5 the potential equation) – shashack Jun 21 '17 at 7:38