soda lime glass

[John_Do]

Hello,

I'm trying to figure out what is the more accurate method to reproduce the soda lime glass.

I tried 2 different ways, one using the refraction channel with data from refractiveindex.info, and one using the fog parameter.

> For the refraction method : the R,G,B refraction channels have differents values according to the transmittance value for each corresponding wavelength: so 0.8554, 0.8882 and 0.8882 in the RGB HDR channels. IOR at 1.5251.
> For the fog method : R,G,B refraction channels at 0.88 ( white ), IOR 1.5251.

Here is a comparison between the two methods.



The "refraction method" produces a really clear glass, a bit too clear for my taste, there is no tint on the edge, while the "fog method", which is more artist-friendly and easy to setup at eyeballing, gives a strongly tinted glass ( although the fog setting could be more subtle here )

So I have 2 questions :

> Is V-ray fully accurate when it comes to grab and use this kind of data ? ( I setted up the reflection / refraction depth at 99 )
> What diffuse color I should use for glass in general ? In these examples I put the same value as in refraction channel ( so 0.88 in the 3 channels ), but is there is a "physically accurate" value like the black for metals ?

[Margarita.Stoeva]

Hello!

The difference between the two approaches shows when shading geometry that has varying thickness. For instance, the soda bottle is thicker at the top, around the neck and the base. Fog color will result in more intense color/darkening at those parts and refraction color will produce the same even result as in all the thin areas.

Here is a quick test with the refractiveindex values you specified (I applied them in refraction color to the left geometry set and fog color to the right set):

001 - Diffuse color: default gray.


002 - Diffuse color: black.


003 - Fog multiplier is lowered to 0.1 (you can change this according to your actual geometry size)


004 - Fog color value is changed from 0.89 to 0.98 (I just wanted more vibrant color look here)

> What diffuse color I should use for glass in general ?

I always use black diffuse for glass-like refractive materials just to skip the energy preservation effect. A physically accurate value will depend on the exact material you want to produce. For instance if you want to shade some minerals like moon stone then appropriate diffuse component could be used (...and a sub-surface shading method).

Is V-ray fully accurate when it comes to grab and use this kind of data ?

It should be in gneral. However you would also need to set your scene correctly because it will effect the final look of the materials too.

I hope this was helpful to you.
Best regards,
Margarita

[John_Do]

Hello,

Thank you for these few examples, it is helpful indeed !