Blackbody

// Blackbody Color Shader
// Blackbody.osl, by Zap Andersson
// Modified: 2021-03-17 by Saul Espinosa for Redshift 3D
// Copyright 2019 Autodesk Inc, All rights reserved. This file is licensed under Apache 2.0 license
//    https://github.com/ADN-DevTech/3dsMax-OSL-Shaders/blob/master/LICENSE.txt
shader Blackbody
[[ string help     = "Modulates a color between two Kelvin temperatures",
   string category = "Utility",
   string label    = "Blackbody Emission"
]]
(
    float  Input = 1.0 [[string page = "1 : Input", float min = 0, float max = 5]],
    float  Min   = 0.0     [[ float min = 0.0, float max = 10000.0, string page = "1 : Input" ]],
    float  Max   = 5000.0  [[ float min = 0.0, float max = 10000.0, string page = "1 : Input" ]],
    float  Intensity = 1.0 [[ float min = 0, float max = 100, string page = "1 : Input" ]],
    int   aces = 0
        [[ string widget = "checkBox",
            string page = "2 : Extra",
            string label = "ACES",
            int connectable = 0 ]],
    output color outColor = 0.0,
)
{
    // ACES sRGB Transform
    matrix aces_tm = matrix(
        0.6131, 0.0701, 0.0206, 0,
        0.3395, 0.9164, 0.1096, 0,
        0.0474, 0.0135, 0.8698, 0,
        0, 0, 0, 1);
    color Col = blackbody(mix(Min, Max, Input));
    color Out = Col * Intensity;
    float r = Out[0], g = Out[1], b = Out[2];
// ACES Output
    if (aces == 0)
    outColor = Out;
    else
    {
    outColor = transform(aces_tm, vector(r,g,b));
    }    
}