<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 username_1 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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