OctaneRender™ Standalone 3.08 TEST 4

[acc24ex]

how do you access toon shaders

[funk]

OTOY devs, there is some kind of colorspace problem with OSL shaders plugged into the normal pin on materials.

If you just output color(0.5, 0.5, 1.0) from your OSL texture, and plug it into a normal pin, the normals are incorrect (eg you will see triangle artifacts on the octane material preview ball). I have to add 2 color correction nodes after it with gamma = 2.2, to get the correct output

I noticed this while playing around with the vray flakes shader. It has an option called "flake normal orientation", which when set to 1, basically outputs color(0.5, 0.5, 1.0)

Regular RGB node to normal pin

OSL RGB to normal pin

[funk]

Shouldn't a "metallic material" with n = 1.5, k = 0, look the same as a glossy material with IOR = 1.5?
The metallic material is shinier. Is this a case of using the wrong fresnel formula again? You've done this in the past and had to switch to non polarised
EDIT: Setting n = 0, and specular = 0.04 (4% = IOR 1.5), is getting much closer to the glossy material (although fresnel is a bit different due to schlick's approximation). So something is wrong with your n/k formula

OTOY Devs,

I did some more testing and it seems the VRay Complex IOR OSL example (https://docs.chaosgroup.com/display/OSL ... nel+shader) matches your metallic material and has the same problem (n = 1.5, k = 0 is more reflective than the glossy mat at IOR 1.5).

I found another site with a different formula (and some hlsl code) for conductors and converted it to OSL. This one looks correct at IOR 1.5
https://seblagarde.wordpress.com/2013/0 ... equations/

I thought it was worth passing this on so you can look into it.

Here is the code converted to OSL. It includes functions for another approximation, along with the vray osl function, so I could compare them.

Code: Select all

// Based on https://seblagarde.wordpress.com/2013/04/29/memo-on-fresnel-equations/
// This seems to be the most accurate (?)

float FresnelDieletricConductor(float Eta, float Etak, float CosTheta)
{  
    float CosTheta2 = CosTheta * CosTheta;
    float SinTheta2 = 1 - CosTheta2;
    float Eta2 = Eta * Eta;
    float Etak2 = Etak * Etak;

    float t0 = Eta2 - Etak2 - SinTheta2;
    float a2plusb2 = sqrt(t0 * t0 + 4 * Eta2 * Etak2);
    float t1 = a2plusb2 + CosTheta2;
    float a = sqrt(0.5 * (a2plusb2 + t0));
    float t2 = 2 * a * CosTheta;
    float Rs = (t1 - t2) / (t1 + t2);

    float t3 = CosTheta2 * a2plusb2 + SinTheta2 * SinTheta2;
    float t4 = t2 * SinTheta2;   
    float Rp = Rs * (t3 - t4) / (t3 + t4);

    //return 0.5 * (Rp + Rs);
    return clamp(0.5 * (Rp + Rs), 0.0, 1.0);
}


// Based on the approximation at https://seblagarde.wordpress.com/2013/04/29/memo-on-fresnel-equations/

float FresnelDieletricConductorApprox(float Eta, float Etak, float CosTheta)
{
    float CosTheta2 = CosTheta * CosTheta;
    float TwoEtaCosTheta = 2 * Eta * CosTheta;

    float t0 = Eta * Eta + Etak * Etak;
    float t1 = t0 * CosTheta2;
    float Rs = (t0 - TwoEtaCosTheta + CosTheta2) / (t0 + TwoEtaCosTheta + CosTheta2);
    float Rp = (t1 - TwoEtaCosTheta + 1) / (t1 + TwoEtaCosTheta + 1);

    //return 0.5 * (Rp + Rs);
    return clamp(0.5 * (Rp + Rs), 0.0, 1.0);
}


// Based on https://docs.chaosgroup.com/display/OSLShaders/Complex+Fresnel+shader

float fresnelVrayComplexIor(float n, float k, float c)
{
    float k2=k*k;
    float rs_num = n*n + k2 - 2*n*c + c*c;
    float rs_den = n*n + k2 + 2*n*c + c*c;
    float rs = rs_num/ rs_den;
     
    float rp_num = (n*n + k2)*c*c - 2*n*c + 1;
    float rp_den = (n*n + k2)*c*c + 2*n*c + 1;
    float rp = rp_num/ rp_den;
     
    return clamp(0.5*( rs+rp ), 0.0, 1.0);
}

float fresnel(float n, float k, float c)
{
    return FresnelDieletricConductor(n, k, c);
    //return FresnelDieletricConductorApprox(n, k, c);
    //return fresnelVrayComplexIor(n, k, c);
}

    
shader FresnelDieletricConductor (
    vector n=vector(1.5, 1.5, 1.5) [[ string description = "Refractive index for red, green, blue wavelengths (f.e. for 0.65, 0.55, 0.45 micrometers)" ]],
    vector k=vector(0.0, 0.0, 0.0) [[ string description = "Extinction coefficient for red, green, blue wavelengths (f.e. for 0.65, 0.55, 0.45 micrometers)" ]],
    output color Col_Out = color(0.5)
)
{
    float thetaCos = abs(dot(-I,N));
    float red=fresnel(n[0], k[0], thetaCos);
    float green=fresnel(n[1], k[1], thetaCos);
    float blue=fresnel(n[2], k[2], thetaCos);
    Col_Out=color(red, green, blue);
}

[bepeg4d]

Hi acc24ex,
just create a new one, or transform one of the existing material into a Toon material:

Then, you need also a Toon light, to be able to render in Toon mode:

Please, have a looka t the attached scene with a simple setup to have the Daylight Sun position linked with a Toon Distant Light position:

toonTest_01.orbx

(542.46 KiB) Downloaded 217 times

ciao beppe

[acc24ex]

cool, I did find the toon shader, but next I wanted to do just the outlines - so it looks like some sort of technical render, just the lights.. and it always looks like it's trying to do the glossy shade of that outline color.. even though specular and all is at 0.. tried ramps, same thing .. like all toons are glossy.. should be an option to turn all of that glossy outline color off

- basically, black outlines on white, if it's not yet implemented, consider that - so we can get a technical illustration out, that would be awesome

[bepeg4d]

Hi acc24ex,
you can set the specular at 0, and switch the Toon Light mode to Camera light:

ciao beppe

[acc24ex]

thanks for the info
..but I had a complex curvy object, and tried that, it looked sort of like this only on some angles, when you move around it always casted the outline color that looked like glossy..
try something curvy..

[acc24ex]

try doing a toon on this to get an outline only.. do the toon light affect this

[bepeg4d]

Hi acc24ex,
you need to play with the Outline Thickness value, but the issue comes with flat surfaces, not with curved surfaces:

Here is a different effect by mixing two different thikness with a mix material:

ciao beppe

[acc24ex]

thanks for the tryout.. so at low angles you get this "shine" overlay that is outline color/thickness.. check the boots on you characters at the bottom.. this is prononuced on this cylinder..

- octane guys, how about it - it will be very useful for archvis and product when you need to do a lineart type render.. tried all settings on the shader couldn't much closer than this