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/*
* Copyright 2018 Blender Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "stdcycles.h"
color log3(color a)
{
return color(log(a[0]), log(a[1]), log(a[2]));
}
color sigma_from_concentration(float eumelanin, float pheomelanin)
{
return eumelanin * color(0.506, 0.841, 1.653) + pheomelanin * color(0.343, 0.733, 1.924);
}
color sigma_from_reflectance(color c, float azimuthal_roughness)
{
float x = azimuthal_roughness;
float roughness_fac = (((((0.245 * x) + 5.574) * x - 10.73) * x + 2.532) * x - 0.215) * x +
5.969;
color sigma = log3(c) / roughness_fac;
return sigma * sigma;
}
shader node_principled_hair_bsdf(color Color = color(0.017513, 0.005763, 0.002059),
float Melanin = 0.8,
float MelaninRedness = 1.0,
float RandomColor = 0.0,
color Tint = 1.0,
color AbsorptionCoefficient = color(0.245531, 0.52, 1.365),
normal Normal = Ng,
string parametrization = "Absorption coefficient",
float Offset = radians(2),
float Roughness = 0.3,
float RadialRoughness = 0.3,
float RandomRoughness = 0.0,
float Coat = 0.0,
float IOR = 1.55,
string AttrRandom = "geom:curve_random",
float Random = 0.0,
output closure color BSDF = 0)
{
/* Get random value from curve in none is specified. */
float random_value = 0.0;
if (isconnected(Random)) {
random_value = Random;
}
else {
getattribute(AttrRandom, random_value);
}
/* Compute roughness. */
float factor_random_roughness = 1.0 + 2.0 * (random_value - 0.5) * RandomRoughness;
float m0_roughness = 1.0 - clamp(Coat, 0.0, 1.0);
float roughness = Roughness * factor_random_roughness;
float radial_roughness = RadialRoughness * factor_random_roughness;
/* Compute absorption. */
color sigma;
if (parametrization == "Absorption coefficient") {
sigma = AbsorptionCoefficient;
}
else if (parametrization == "Melanin concentration") {
/* Randomize melanin. */
float factor_random_color = 1.0 + 2.0 * (random_value - 0.5) * RandomColor;
float melanin = Melanin * factor_random_color;
/* Map melanin 0..inf from more perceptually linear 0..1. */
melanin = -log(max(1.0 - melanin, 0.0001));
/* Benedikt Bitterli's melanin ratio remapping. */
float eumelanin = melanin * (1.0 - MelaninRedness);
float pheomelanin = melanin * MelaninRedness;
color melanin_sigma = sigma_from_concentration(eumelanin, pheomelanin);
/* Optional tint. */
color tint_sigma = sigma_from_reflectance(Tint, radial_roughness);
sigma = melanin_sigma + tint_sigma;
}
else if (parametrization == "Direct coloring") {
sigma = sigma_from_reflectance(Color, radial_roughness);
}
else {
/* Fallback to brownish hair, same as defaults for melanin. */
sigma = sigma_from_concentration(0.0, 0.8054375);
}
BSDF = principled_hair(Normal, sigma, roughness, radial_roughness, m0_roughness, Offset, IOR);
}
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