<p>I am reading a paper and there is a part I don't understand:
<a href="https://i.sstatic.net/anl7u.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/anl7u.png" alt="enter image description here"></a></p>

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

CC BY-SA 4.0
2019-01-31T14:00:37.833Z
I think that it does depend on it, it just does not depend on $\phi$. Where's the reference from?
lightxbulb
CC BY-SA 4.0
2019-01-31T20:47:00.017Z
https://drive.google.com/file/d/0BzvWIdpUpRx_d09ndGVjNVJzZjA/view, from page 4.
TIANLUN ZHU
CC BY-SA 4.0
2019-01-31T21:39:16.407Z
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.
lightxbulb
<brdf><pbr>
confused on isotropic BRDF
TIANLUN ZHU
# confused on isotropic BRDF

(Asked by: username_0 on 2019-01-26)

I am reading a paper and there is a part I don't understand:
[![enter image description here](https://i.sstatic.net/anl7u.png)](https://i.sstatic.net/anl7u.png)

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

**Tags:** brdf, pbr

> **Comments:**
> **username_1**: I think that it does depend on it, it just does not depend on $\phi$. Where's the reference from?  
> **username_0**: https://drive.google.com/file/d/0BzvWIdpUpRx_d09ndGVjNVJzZjA/view, from page 4.  
> **username_1**: 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.  

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## 0 answers

