Thin film OSL shader

[Leeds3D]

loving this shader but i'm having a few crashes using it (similarly with the osl glass shader - http://www.rensheeren.com/blog/osl-archglass/ but only now we've updated from 3ds max 2016 to 2019 - it didn't crash at all in 2016). any pointers or ideas i can look at to help? at the moment either in new scenes or adding this osl shader to current proects i get random crashes at the point i hit render.

[simmsimaging]

Thanks for the reply Vlado. I went back to the file to grab a screen shot and now I can see it. There is also a rollout for OSL include Paths that wasn't showing up before too. I am *reasonably* certain that it was not just me failing to scroll down far enough - that was the first thing I checked. Anyway, only thing that changed is a reboot of the computer in between. Seems solved for now anyway.

[vlado]

This works fine for me actually. Can you show me a screengrab of the material editor?

Best regards,
Vlado

[simmsimaging]

Testing this out with the scene Vlado posted (Vray Next in Max 2020) I am wondering if I'm missing something: I do not see any parameters for the OSL texture. There is no shader parameter rollout and no apparent way to edit the thickness etc. Is there something I need to do to expose those controls in Max?

[padre.ayuso]

I just tried this and it is awesome! Thanks Vlado!!!!

My two cents, I'd definitely add it to the VRayMTL. However, if you are going to start doing a more complex material for VRay 4.0 or something, something that is more "Advanced user" sort of speak, then maybe you can create a second type of VRay Material and eventually I'll guess the one will fade away and the most used will win and stay.

[sharktacos]

Vlado et al.,

As you consider adding clearcoat to the VrayMtl, it would be worth taking a look at the PxrSurface shader. It has a lot of physically based parameters included for this, including Energy Compensation, Iridescence, Thin Film Thickness, Layer thickness, and Absorption Tint.
https://rmanwiki.pixar.com/display/R...ce-Iridescence

I would add this to th VrayMtl for purposes of physically correct energy conservation. As Art48 says, awesome > clutter.

[sharktacos]

Art48,
What would be the advantage of having it in the VrayMtl? Personally I would rather see a clearcoat / secondary reflection section added to the VrayMtl, but that's just me.

[Art48]

I third it. Although I'd rather see it inside the VRayMtl itself. F*** clutter. This is professional software where you just have to know what buttons to push and what checkboxes to set to achieve your goal. If you want a very beginner-friendly version just make a VRay-Lite or something similar.

[Morbid Angel]

Instead of adding this to the VrayMtl (if folks are worried about clutter), how about having this as a new VrayTexture that ships with Vray?

I second that!

[sharktacos]

Instead of adding this to the VrayMtl (if folks are worried about clutter), how about having this as a new VrayTexture that ships with Vray?

[vlado]

Which V-Ray version and which OS?

Best regards,
Vlado

[DjordjeIlic]

Hi everyone.

I looking for some iridescent reflection....I tried OSL thin film,
but not working in Maya 2016-sp6.same osl working very well in max.

Thank you!
Djordje

[Macker]

Any news on building this into the Vray Shader? (perhaps under its own tab?)

I'm sure this could be used to create dichroic glass, could it not?

[sharktacos]

yup same here...any ideas?

Don't know if this is relevant in Max, but in Maya the outputs and results need to be called "color". Try this:

/* Amplitude reflection coefficient (s-polarized) */
float rs(float n1, float n2, float cosI, float cosT) {
    return (n1 * cosI - n2 * cosT) / (n1 * cosI + n2 * cosT);
}
 
/* Amplitude reflection coefficient (p-polarized) */
float rp(float n1, float n2, float cosI, float cosT) {
    return (n2 * cosI - n1 * cosT) / (n1 * cosT + n2 * cosI);
}
 
/* Amplitude transmission coefficient (s-polarized) */
float ts(float n1, float n2, float cosI, float cosT) {
    return 2 * n1 * cosI / (n1 * cosI + n2 * cosT);
}
 
/* Amplitude transmission coefficient (p-polarized) */
float tp(float n1, float n2, float cosI, float cosT) {
    return 2 * n1 * cosI / (n1 * cosT + n2 * cosI);
}
 
// cosI is the cosine of the incident angle, that is, cos0 = dot(view angle, normal)
// lambda is the wavelength of the incident light (e.g. lambda = 510 for green)
// From http://www.gamedev.net/page/resources/_/technical/graphics-programming-and-theory/thin-film-interference-for-computer-graphics-r2962
float thinFilmReflectance(float cos0, float lambda, float thickness, float n0, float n1, float n2) {
    //float PI=3.1415926535897932384626433832795;
    float PI=M_PI;

    // compute the phase change term (constant)
    float d10 = (n1 > n0) ? 0 : PI;
    float d12 = (n1 > n2) ? 0 : PI;
    float delta = d10 + d12;
     
    // now, compute cos1, the cosine of the reflected angle
    float sin1 = pow(n0 / n1, 2) * (1 - pow(cos0, 2));
    if (sin1 > 1) return 1.0; // total internal reflection
    float cos1 = sqrt(1 - sin1);
     
    // compute cos2, the cosine of the final transmitted angle, i.e. cos(theta_2)
    // we need this angle for the Fresnel terms at the bottom interface
    float sin2 = pow(n0 / n2, 2) * (1 - pow(cos0, 2));
    if (sin2 > 1) return 1.0; // total internal reflection
    float cos2 = sqrt(1 - sin2);
     
    // get the reflection transmission amplitude Fresnel coefficients
    float alpha_s = rs(n1, n0, cos1, cos0) * rs(n1, n2, cos1, cos2); // rho_10 * rho_12 (s-polarized)
    float alpha_p = rp(n1, n0, cos1, cos0) * rp(n1, n2, cos1, cos2); // rho_10 * rho_12 (p-polarized)
     
    float beta_s = ts(n0, n1, cos0, cos1) * ts(n1, n2, cos1, cos2); // tau_01 * tau_12 (s-polarized)
    float beta_p = tp(n0, n1, cos0, cos1) * tp(n1, n2, cos1, cos2); // tau_01 * tau_12 (p-polarized)
         
    // compute the phase term (phi)
    float phi = (2 * PI / lambda) * (2 * n1 * thickness * cos1) + delta;
         
    // finally, evaluate the transmitted intensity for the two possible polarizations
    float ts = pow(beta_s, 2) / (pow(alpha_s, 2) - 2 * alpha_s * cos(phi) + 1);
    float tp = pow(beta_p, 2) / (pow(alpha_p, 2) - 2 * alpha_p * cos(phi) + 1);
     
    // we need to take into account conservation of energy for transmission
    float beamRatio = (n2 * cos2) / (n0 * cos0);
     
    // calculate the average transmitted intensity (if you know the polarization distribution of your
    // light source, you should specify it here. if you don't, a 50%/50% average is generally used)
    float t = beamRatio * (ts + tp) / 2;
     
    // and finally, derive the reflected intensity
    return 1 - t;
}
 
shader irridescence
[[ string description = "Thin film coating shader. Use as reflection color for the material, with Fresnel for the material OFF (this texture computes its own Fresnel)" ]]
(   
 float thicknessMin = 250 [[ string description = "Minimum thickness of the film, in nm" ]],
 float thicknessMax = 400 [[ string description = "Maximum thickness of the film, in nm" ]],
 string thickness = "test.png" [[ string description = "Texture map (usually noise) that determines the thickness of the film as fraction between the min and max" ]],
 float nmedium = 1 [[ string description = "Refractive index of the outer medium (typically air)" ]], // approximate refractive index of air   
 float nfilm = 1.5 [[ string description = "Refractive index of the thin film itself" ]] , // approximate refractive index of water   
 float ninternal = 1 [[ string description = "Refractive index of the material below the film" ]], // approximate refractive index of the lower material
 output color result = 0   
)   
{   
 float cos0 = abs(dot(I , N));
  
 color thickTex=texture(thickness, u, v);
 float t=(thickTex[0]+thickTex[1]+thickTex[2])/3.0;
 float thick=thicknessMin*(1.0-t)+thicknessMax*t;
  
 float red=thinFilmReflectance(cos0, 650, thick, nmedium, nfilm, ninternal);
 float green=thinFilmReflectance(cos0, 510, thick, nmedium, nfilm, ninternal);
 float blue=thinFilmReflectance(cos0, 475, thick, nmedium, nfilm, ninternal);
  
 result=color(red, green, blue);
}

[Morbid Angel]

Seems to broken on 2015?

I get this error
In the material compiler output
Could not compile shader J:\Jobs\46761M_Mazda2Headlight_CP\3d\Projects\Maps \irridescence.osl (OSL to OSO)

yup same here...any ideas?