Specular material, color vs. transparency

[Proupin]

I don't understand the current specular material in regards to the transmission channel... how is it that the color is linked to the transparency, in such a way that you can't make a white, semi-transparent material... or a black semi-transparent material... I understand gray produces a semi-transparent material but it's gray, not white or black... So in essence the Luminosity of the color determines the transparency, which is akward, isn't it...

[Proupin]

Doesn't anyone have a clue of what I'm talking about?

[matej]

In reality transparency is linked to how much is light influenced when passing through a medium - ie. transparency is controlled by properties of the material like absorption, transmission & reflection.

Octane is a physically correct renderer. The HSV color picker of the transmission parameter controls:

* which color (=wavelength) does the material absorb - hue
* how much of this color is absorbed - saturation
* and how much of all the other colors are absorbed - value.

So, saturation controls the "amount of transparency", hue controls the "color of the material" and value controls both. Think of the color picker not as defining color, but controlling these three parameters. You will see that you can't have a semi-transparent black material, because black means that all the wavelengths are absorbed at 100% = no transparency. Equally, you can't have a semi-transparent white material.

In reality there's no such thing as semi-transparent black material. Clear glass for drinking utensils is also not white, for example, it's more like a very subtle gray - because it transmits almost 100% of light, but some of it is absorbed. You also can't have a very saturated material, that is strongly transparent, because by rising color saturation you trade off transparency - you actually say that 100% of this wavelength is absorbed = less transparency.

Anyway, this is my amateur explanation / interpretation

[Proupin]

Hmmm... I prefer calling it Physically BASED, not "correct"... after all, Snell's law is not implemented AT ALL (internal reflections etc), and Octane has no clue whether the ray is In the medium or our of it to produce internal reflection to begin with... there is no real absorption either. Anyway, you are probably right about the hsv correspondence, I'll have to look it up, thanks!

EDIT: I posted an image of a white plastic container, see how it's opaque in a way, but still its tone is white! There are some tuppers around my kitchen that can confirm that

[matej]

Yeah, physically based is a better definition.
I haven't done much glass stuff with Octane, or layers of transparent objects, so I don't have much experience there... Post if you get any good results

[radiance]

volumetrics are planned for v2.0, so no SSS yet for effects like this...

although the diffuse transmission *might* be used but you won't get the same result.

Radiance

[Perdition]

Ehm, sorry for the noob question but, where can I find this HSV color picker? I only see the RGB one...

[radiance]

Ehm, sorry for the noob question but, where can I find this HSV color picker? I only see the RGB one...

there is no HSV color picker, i think it's a typo by matej,

Radiance

[matej]

Actually it's not a typo, just the way I related material parameters to picker parameters (I couldn't explain what I meant in RGB space)

But, yeah, there is no HSV picker in Octane - maybe it would be good to have it (or just 3 sliders that act as converters RGB<->HSV)?

[radiance]

Actually it's not a typo, just the way I related material parameters to picker parameters (I couldn't explain what I meant in RGB space)

But, yeah, there is no HSV picker in Octane - maybe it would be good to have it (or just 3 sliders that act as converters RGB<->HSV)?

yeah, that and the other 5000 things you request lol

Radiance