POV-Ray : Newsgroups : povray.general : Glass for v3.8 finish features : Re: Glass for v3.8 finish features Server Time
19 Aug 2022 04:18:59 EDT (-0400)
  Re: Glass for v3.8 finish features  
From: Alain Martel
Date: 5 Aug 2022 13:29:07
Message: <62ed5363$1@news.povray.org>
Le 2022-08-04 à 14:12, Chris R a écrit :
> Alain Martel <kua### [at] videotronca> wrote:
>> Le 2022-08-02 à 11:29, Chris R a écrit :
>>> Whenever I create a scene that contains objects made of glass, I spend a lot of
>>> time tweaking the various pigment, finish, and interior parameters of the
>>> material to try and get something that looks realistic.  Sometimes I start with
>>> what I can find in glass.inc, but it doesn't appear to have been updated since
>>> v3.5.
>>>
>>> Has anyone worked on something similar to RC3Metal for glass that takes
>>> advantage of all of the new finish features in later versions?  It might be
>>> something I'd be willing to explore, but I don't have a great grasp on how all
>>> of combinations, including fresnel interact, so it's going to be hit and miss.
>>>
>>> Thanks,
>>>
>>> -- Chris R.
>>>
>>>
>>
>> Normally, for a transparent object having an IOR, you use reflection{1
>> fresnel} to control the reflectivity. There is usually no need to use
>> another value here.
>> Fresnel reflection depends entirely on the ratio between the ior on each
>> sides of the surface and the angle of incidence. A ratio of 1 mean NO
>> reflection. A standalone object without an interior defining an ior
>> different from 1 will also show no fresnel reflection.
>>
>> When the fresnel keyword is present, it always default to ON.
>> falloff and exponent should be left to their default values. Don't use
>> those.
>> Do not use metallic.
>>
>> Then, you should also use the fresnel option for the highlights. Need
>> the latest version. IIRC, it was not implemented in version 3.7, but is
>> supported in the latest V1.8 beta.
>> Examples : specular 0.7 fresnel roughness 0.001, phong 0.7 fresnel
>> phong_size 500
>>
>> Also, you should use transmit 1 or filter 1 as your pigment.
>> If you want the object to be coloured, use fading in the interior
>> statement :
>> interior{ior 1.5 fade_color rgb<1, 0.6, 0.6> fade_distance 1 fade_power
>> 1001}// A pink object.
>> Adjust fade_distance for the dimension and scale of your object. It's
>> easily the most important parameter when using fading colours in an
>> interior.
>>
>> ALWAYS use conserve_energy.
>>
>> Sample glass :
>> texture{
>>   pigment{rgbt 1}
>>   finish{specular 1 roughness 0.001 fresnel
>>    ambient 0 diffuse 0
>>    reflection{ 1 fresnel }
>>    conserve_energy
>>   }
>> }
>> interior{ ior 1.5 //typical glass IOR
>>   fade_color rgb<0.9, 1, 0.9>//slightly greenish
>>   fade_distance 2 // Adjust to the size and scale of the object
>>   fade_power 1001}
> 
> Thanks for the insights.  I am trying them out now.
> 
> I don't have a good understanding of when to use the albedo keywork for specular
> and diffuse reflection.  I note that you do not use it above.
> 
> -- Chris R.
> 
> 

You use albedo when you also use a brilliance that differs from the 
default of 1.

As I did not use brilliance in my example, it was not useful to use albedo.

Example of the use of albedo and fresnel with an opaque pigment :

pigment{rgb< 0.7, 1, 0.2>}
finish{
	brilliance 10 //high brilliance for a very highly polished surface
	diffuse albedo 0.7 // albedo needed to have correct illumination
	specular albedo 1 roughness 0.01// albedo also needed due to the high 
brilliance
// I like to put the roughness on the same line as specular as they work 
together
// Same thing for phong and phong_size.
	fresnel // have the IOR also affect the highlights

	reflection{1 fresnel}
	}
interior{ior 1.7}


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