Specular material: reflection and transmision?

General questions about Indigo, the scene format, rendering etc...
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walnist
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Specular material: reflection and transmision?

Post by walnist » Thu Nov 19, 2015 2:20 am

Hi,
i'm trying to model a realistic human eye, using a physiological eye model including lenses, IORs etc. and i'm not using any exporter but generating indigo script files using a python program (the model is parameterized).

I'm trying to better understand how the reflective type of materials work, in particular to model the cornea which has material properties which are between glass and liquids.

So far the glossy-transparent worked reasonably well, but i'm now having a scene where the image of a light source ("glint") should appear reflected in the eyes, but it doesn't because the light source is shining in the eyes through a mirror.

I am under the impression that the glossy-transparent specular highlight works like in the Phong model, and it shows highlights only generated by direct rays (not reflected) is that correct?

If i want to get the glint of the reflected light source, it seems i have to use the Specular material, but i haven't found a proper way to control which percentage of the incoming light power is reflected and which is refracted.
My current workaround is to use a Blend type which includes a purely reflecting Specular material and a purely refracting Specular + transparent + Arch glass; i can then use the Blend factor to control the reflected energy vs the refracted one.
But this renders extremely slow.

Is there a proper way for the Specular material to set Reflected and Refracted ratios?
Thanks,
Walter

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CTZn
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Re: Specular material: reflection and transmision?

Post by CTZn » Fri Nov 20, 2015 5:53 pm

Hi, fascinating project !

I'm pretty sure there's only IOR to manage that, it's got electrolytes. I mean, it's the way known as correct to do what you want, unless if I'm mistaking.

How far have materials been developed ? Are you using absorptions, scatterings ? Is all the Indigo vocabulary straight between us ? I'm not into physics either but would sure like to know more.

Images welcome :)
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CTZn
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Re: Specular material: reflection and transmision?

Post by CTZn » Fri Nov 20, 2015 6:23 pm

I think you may be looking for a Fresnel function; specular and glossy transparent don't have that one. Phong does, but it's Phong.

Perhaps a justified request ?
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Polinalkrimizei
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Re: Specular material: reflection and transmision?

Post by Polinalkrimizei » Sun Nov 22, 2015 9:33 am

Please post some pics, this project sounds AMAZING!!

walnist
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Re: Specular material: reflection and transmision?

Post by walnist » Fri Nov 27, 2015 4:28 am

Thanks guys!

The way i understand it, IOR controls only the angle of refraction (i.e. how much a "lens distortion" effect) the liquid or glass surface has; this however does not control the amount of light which gets reflected vs the amount which gets refracted (that'd be reflectance vs transmission of the surface).

Is there anybody of the Indigo developers here who could answer my question?
Cheers,

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OnoSendai
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Re: Specular material: reflection and transmision?

Post by OnoSendai » Fri Nov 27, 2015 11:42 pm

walnist wrote:Thanks guys!

The way i understand it, IOR controls only the angle of refraction (i.e. how much a "lens distortion" effect) the liquid or glass surface has; this however does not control the amount of light which gets reflected vs the amount which gets refracted (that'd be reflectance vs transmission of the surface).

Is there anybody of the Indigo developers here who could answer my question?
Cheers,
IOR controls the amount of reflection as well, via the Fresnel equation.

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