On Fri, 03 Jul 2015 15:35:51 +0200, clipka <ano### [at] anonymousorg> wrote:

> Am 03.07.2015 um 05:08 schrieb Nekar Xenos:
>
>>>> If you are using fresnel, is it valid (from a PBR point of view) to  
>>>> even
>>>> scale the results using a maximum reflection other than 1?
>>>
>>> Absolutely - if, for instance, your surface is littered with
>>> non-specular material at a microscopic level. Fine rust on iron steel,
>>> for instance, or a thin coating of dust.
>>>
>>> In those cases it might be better, however, to use an average of two
>>> materials.
>>>
>>
>> What about plastic? It reflects, but it's not highly reflective. I don't
>> think I would go higher than 0.5 maximum reflection on plastic.
>
> For plastics - and actually any material that's neither metallic nor  
> coated - I think heavily blurred reflections and a well-chosen ior are  
> the key, not reducing the reflection maximum.
>
> With a high ior, the maximum reflection only occurs when viewing the  
> material almost edge-on. And with blurred reflections, even there the  
> maximum isn't truly achieved, as the effective reflection brightness is  
> tuned down by averaging in reflections at a less shallow effective angle.
>
> BTW, the ior of most plastics is in the range from 1.5 to 1.6.
>

So a shiny plastic has a high ior I assume. Then it makes sense.

-- 
-Nekar Xenos-

Post a reply to this message

> So a shiny plastic has a high ior I assume. Then it makes sense.

What makes a plastic shiny or not is usually the geometric finish on the 
surface, not anything to do with the material itself. It all depends on 
the surface finish of the mould tool that was used to make the part. It 
can be anything from high polished (to give a high gloss finish) to a 
very fine texture (to give varying degrees of matt finish) to a large 
patterned texture for something like a leather effect on car trim.

Post a reply to this message

Thomas de Groot <tho### [at] degrootorg> wrote:

>
> Now, that is a comprehensive tutorial about do's and dont's. Thanks
> indeed Christoph.
>

I second that! So much wonderful/useful information--and in only one post!!

Post a reply to this message