MarbleShader

/*
 * VeinedMarble.osl by Shane Ambler
 * from https://github.com/sambler/osl-shaders
 * 
 * original script from -
 * http://www.renderman.org/RMR/RMRShaders.html
 *
 * veinedmarble.sl -- surface shader for a nice veined marble.
 *
 * DESCRIPTION:
 *   Makes solid marble texture with strong veins.  The "veincolor" parameter
 *   controls the color of the veins.  The background color is given by the
 *   surface color (Cs).
 * 
 * PARAMETERS:
 *   Ka, Kd, Ks, roughness, specularcolor - same as plastic
 *   veinfreq - controls fhe lowest frequency of the color veins
 *   veinlevels - how many "levels" of vein tendrills it has
 *   warpfreq - lowest frequency of the turbulent warping in the marble
 *   warping - controls how much turbulent warping there will be
 *   veincolor - the color of the veins
 *   sharpness - controls how sharp or fuzzy the veins are (higher = sharper)
 *
 *
 * AUTHOR: Larry Gritz, the George Washington University
 *         email: gritz AT seas DOT gwu DOT edu 
 * This file is licensed under Apache 2.0 license
 * HISTORY:
 *
 * last modified  29 Jun 1994 by Larry Gritz
 * 2012-12-19 converted to blender osl shader by Shane Ambler
 * 2020-4-27 converted to a Redshift Shader by Saul Espinosa, added coating Microfact GGX & Oren Nayer closure, 
 * new defaults, min/max values, label and page metadata. 
 * 2022-03-08 Added World, Object space controls for the Noise
 */
shader VeinedMarble 
[[  string help = "Marble Closure Based Material",
    string label = "Marble" ]]
(
// Input Paramaters
        color diffuse_color = color(0.946,0.788,0.829)
        [[
            string label = "Diffuse Color", 
            string page = "Diffuse"
        ]],
        float diffuse_weight = 0.8
        [[
            string label = "Diffuse Weight" ,
            string page = "Diffuse",
            float min = 0, float max = 1
        ]],
        float diffuse_rough = 0.0
        [[
            string label = "Diffuse Roughness" ,
            string page = "Diffuse",
            float min = 0, float max = 1
        ]],
        color SpecularColor = color(1.0)
        [[
            string page = "Specular",
            string label = "Specular Color"
        ]],
        float SpecularWeight = 1.0
        [[
            string label = "Specular Weight" ,
            string page = "Specular",
            float min = 0, float max = 1
        ]],
        float Roughness = 0.4
        [[
            string label = "Roughness" ,
            string page = "Specular",
            float min = 0, float max = 1
        ]],
        float IOR = 1.48
        [[
            string label = "IOR",
            string page = "Specular",
            float min = 0, float max = 25
        ]],
        color coat_color = color(1.0)
        [[
            string label = "Coat Color",
            string page = "Coat",
        ]],
        float coat_weight = 1.0
        [[
            string label = "Coat Weight" ,
            string page = "Coat",
            float min = 0, float max = 1
        ]],
        float coat_roughness = 0.005
        [[
            string label = "Coat Roughness" ,
            string page = "Coat",
            float min = 0, float max = 1
        ]],
        float coat_IOR = 1.52
        [[
            string label = "Coat IOR" ,
            string page = "Coat",
            float min = 0, float max = 25
        ]],
        color VeinColor = color(0.663, 0.319, 0.371)
        [[
            string label = "Vein Color",
            string page = "Marble Vein"
        ]],
        float VeinFreq = 1.0
        [[
            string label = "Vein Frequency" ,
            string page = "Marble Vein",
            float min = 0, float max = 10
        ]],
        float VeinLevels = 2.0
        [[
            string label = "Vein Levels" ,
            string page = "Marble Vein",
            float min = 0, float max = 25
        ]],
        float WarpFreq = 1.0
        [[
            string label = "Warp Frequency" ,
            string page = "Marble Vein",
            float min = 0, float max = 25
        ]],
        float Warping = 0.5
        [[
            string label = "Vein Warping" ,
            string page = "Marble Vein",
            float min = 0, float max = 25
        ]],
        float Sharpness = 8.0
        [[
            string label = "Vein Sharpness" ,
            string page = "Marble Vein",
            float min = 0, float max = 25
        ]],
        int Space = 1
        [[
            string page = "Co-ordinates",
            string widget = "mapper",
            string options = "World:0|Object:1|Fixed:2",
            int connectable = 0
        ]],
        vector Origin = 0
        [[
            string page = "Co-ordinates"
        ]],
// Output Closure        
        output closure color outColor = diffuse(N) )
{
#define snoise(x) (2*noise(x)-1)
    color Ct;
    point Nf;
    point PP, offset;
    float i, turb, freq, j;
    float turbsum;
    if (Space == 0)
        PP = P + Origin;
    else if (Space == 1)
        PP = transform("object", P) + Origin;
    else
        PP = Origin;
    /* perturb the lookup */
    freq = 1;
    offset = 0;
    for (i = 0;  i < 6;  i += 1) {
        offset += 2 * Warping * ( noise (WarpFreq * freq * PP) - 0.5)  / freq;
        freq *= 2;
    }
    PP += offset;
    /* Now calculate the veining function for the lookup area */
    turbsum = 0;  freq = 1;
    PP *= VeinFreq;
    for (i = 0;  i < VeinLevels;  i += 1) {
        turb = abs (snoise (PP));
        turb = pow (smoothstep (0.8, 1, 1 - turb), Sharpness) / freq;
        turbsum += (1-turbsum) * turb;
        freq *= 3;
        PP *= 3;
    }
    color Out = mix (diffuse_color, VeinColor, turbsum);
    Nf = normalize(N);
    outColor = Out * diffuse_weight * oren_nayar(Nf, diffuse_rough);
    outColor += (SpecularColor * SpecularWeight * microfacet("ggx",Nf,Roughness,IOR,0)) + (coat_color * coat_weight * microfacet("ggx",Nf,coat_roughness,coat_IOR,0));
}