<p>Dielectric materials (which is what you get when metalness is 0) don't exhibit a mirror-like effect. Think of a sheet of smooth, non-transparent plastic. Real-life mirrors are panes of glass or transparent plastic covered with a thin layer of metal. Try a white base colour (1,1,1) and full metalness (1) instead.</p>

<p>As Hubble pointed out in his comment, Unity won't do full ray tracing for you out of the box, but it should be able to do some approximation with screen-space reflections and local reflection probes.</p>

CC BY-SA 4.0
2019-03-02T22:57:50.327Z
2019-03-02T22:57:50.327Z
IneQuation
<p>Currently I am learning PBR by Unity3D. I find that even I turn the smoothness to 1, I can still see the diffuse lighting effect, which does not make any sense to me.</p>

<p>Imagine I trace a ray from my eye to the mirror, and I do importance sampling based on the material's brdf, there are only two options,  hit the light source or not. However, I find that if I set the metallic to be 0 and smoothness to 1, there will have large amount of area illuminated.</p>

<p><a href="https://i.sstatic.net/1J2PH.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/1J2PH.png" alt="enter image description here"></a></p>

CC BY-SA 4.0
2019-03-02T07:17:36.403Z
Unity is a real-time engine, it doesn't do ray tracing for you out of the box.
Hubble
<pbr><unity><microfacet>
Why can I see the diffuse lighting effect on a perfect mirror?
TIANLUN ZHU
# Why can I see the diffuse lighting effect on a perfect mirror?

(Asked by: username_0 on 2019-03-02)

Currently I am learning PBR by Unity3D. I find that even I turn the smoothness to 1, I can still see the diffuse lighting effect, which does not make any sense to me.

Imagine I trace a ray from my eye to the mirror, and I do importance sampling based on the material's brdf, there are only two options, hit the light source or not. However, I find that if I set the metallic to be 0 and smoothness to 1, there will have large amount of area illuminated.

[![enter image description here](https://i.sstatic.net/1J2PH.png)](https://i.sstatic.net/1J2PH.png)

**Tags:** pbr, unity, microfacet
> **Comments:**
> **username_1**: Unity is a real-time engine, it doesn't do ray tracing for you out of the box.  

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## 1 answers

### Answer by username_2 on 2019-03-02. Score: 3 | Accepted answer

Dielectric materials (which is what you get when metalness is 0) don't exhibit a mirror-like effect. Think of a sheet of smooth, non-transparent plastic. Real-life mirrors are panes of glass or transparent plastic covered with a thin layer of metal. Try a white base colour (1,1,1) and full metalness (1) instead.

As Hubble pointed out in his comment, Unity won't do full ray tracing for you out of the box, but it should be able to do some approximation with screen-space reflections and local reflection probes.


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