I am reading a paper and there is a part I don't understand: enter image description here

I am wondering why the isotropic BRDF only depends on the view direction and roughness? Why is the light direction not related?

  • $\begingroup$ I think that it does depend on it, it just does not depend on $\phi$. Where's the reference from? $\endgroup$
    – lightxbulb
    Jan 31, 2019 at 14:00
  • $\begingroup$ drive.google.com/file/d/0BzvWIdpUpRx_d09ndGVjNVJzZjA/view, from page 4. $\endgroup$ Jan 31, 2019 at 20:47
  • $\begingroup$ The GGX distribution term they are referring to doesn't take $l$ as argument. However you can see that they do have other terms that take $l$ into account. $\endgroup$
    – lightxbulb
    Jan 31, 2019 at 21:39


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