(function (global, factory) {
  if (typeof define === "function" && define.amd) {
    define(["exports", "../ShaderNode.js"], factory);
  } else if (typeof exports !== "undefined") {
    factory(exports, require("../ShaderNode.js"));
  } else {
    var mod = {
      exports: {}
    };
    factory(mod.exports, global.ShaderNode);
    global.BSDFs = mod.exports;
  }
})(typeof globalThis !== "undefined" ? globalThis : typeof self !== "undefined" ? self : this, function (_exports, _ShaderNode) {
  "use strict";

  Object.defineProperty(_exports, "__esModule", {
    value: true
  });
  _exports.getDistanceAttenuation = _exports.V_GGX_SmithCorrelated = _exports.RE_Direct_Physical = _exports.PhysicalLightingModel = _exports.F_Schlick = _exports.D_GGX = _exports.BRDF_Specular_GGX = _exports.BRDF_Lambert = void 0;
  var F_Schlick = new _ShaderNode.ShaderNode(function (inputs) {
    var f0 = inputs.f0,
        f90 = inputs.f90,
        dotVH = inputs.dotVH; // Original approximation by Christophe Schlick '94
    // float fresnel = pow( 1.0 - dotVH, 5.0 );
    // Optimized variant (presented by Epic at SIGGRAPH '13)
    // https://cdn2.unrealengine.com/Resources/files/2013SiggraphPresentationsNotes-26915738.pdf

    var fresnel = (0, _ShaderNode.exp2)((0, _ShaderNode.mul)((0, _ShaderNode.sub)((0, _ShaderNode.mul)(-5.55473, dotVH), 6.98316), dotVH));
    return (0, _ShaderNode.add)((0, _ShaderNode.mul)(f0, (0, _ShaderNode.sub)(1.0, fresnel)), (0, _ShaderNode.mul)(f90, fresnel));
  }); // validated

  _exports.F_Schlick = F_Schlick;
  var BRDF_Lambert = new _ShaderNode.ShaderNode(function (inputs) {
    return (0, _ShaderNode.mul)(_ShaderNode.RECIPROCAL_PI, inputs.diffuseColor); // punctual light
  }); // validated

  _exports.BRDF_Lambert = BRDF_Lambert;
  var getDistanceAttenuation = new _ShaderNode.ShaderNode(function (inputs) {
    var lightDistance = inputs.lightDistance,
        cutoffDistance = inputs.cutoffDistance,
        decayExponent = inputs.decayExponent;
    return (0, _ShaderNode.cond)((0, _ShaderNode.and)((0, _ShaderNode.greaterThan)(cutoffDistance, 0), (0, _ShaderNode.greaterThan)(decayExponent, 0)), (0, _ShaderNode.pow)((0, _ShaderNode.saturate)((0, _ShaderNode.add)((0, _ShaderNode.div)((0, _ShaderNode.negate)(lightDistance), cutoffDistance), 1.0)), decayExponent), 1.0);
  }); // validated
  //
  // STANDARD
  //
  // Moving Frostbite to Physically Based Rendering 3.0 - page 12, listing 2
  // https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf

  _exports.getDistanceAttenuation = getDistanceAttenuation;
  var V_GGX_SmithCorrelated = new _ShaderNode.ShaderNode(function (inputs) {
    var alpha = inputs.alpha,
        dotNL = inputs.dotNL,
        dotNV = inputs.dotNV;
    var a2 = (0, _ShaderNode.pow2)(alpha);
    var gv = (0, _ShaderNode.mul)(dotNL, (0, _ShaderNode.sqrt)((0, _ShaderNode.add)(a2, (0, _ShaderNode.mul)((0, _ShaderNode.sub)(1.0, a2), (0, _ShaderNode.pow2)(dotNV)))));
    var gl = (0, _ShaderNode.mul)(dotNV, (0, _ShaderNode.sqrt)((0, _ShaderNode.add)(a2, (0, _ShaderNode.mul)((0, _ShaderNode.sub)(1.0, a2), (0, _ShaderNode.pow2)(dotNL)))));
    return (0, _ShaderNode.div)(0.5, (0, _ShaderNode.max)((0, _ShaderNode.add)(gv, gl), _ShaderNode.EPSILON));
  }); // validated
  // Microfacet Models for Refraction through Rough Surfaces - equation (33)
  // http://graphicrants.blogspot.com/2013/08/specular-brdf-reference.html
  // alpha is "roughness squared" in Disney’s reparameterization

  _exports.V_GGX_SmithCorrelated = V_GGX_SmithCorrelated;
  var D_GGX = new _ShaderNode.ShaderNode(function (inputs) {
    var alpha = inputs.alpha,
        dotNH = inputs.dotNH;
    var a2 = (0, _ShaderNode.pow2)(alpha);
    var denom = (0, _ShaderNode.add)((0, _ShaderNode.mul)((0, _ShaderNode.pow2)(dotNH), (0, _ShaderNode.sub)(a2, 1.0)), 1.0); // avoid alpha = 0 with dotNH = 1

    return (0, _ShaderNode.mul)(_ShaderNode.RECIPROCAL_PI, (0, _ShaderNode.div)(a2, (0, _ShaderNode.pow2)(denom)));
  }); // validated
  // GGX Distribution, Schlick Fresnel, GGX_SmithCorrelated Visibility

  _exports.D_GGX = D_GGX;
  var BRDF_Specular_GGX = new _ShaderNode.ShaderNode(function (inputs) {
    var lightDirection = inputs.lightDirection,
        f0 = inputs.f0,
        f90 = inputs.f90,
        roughness = inputs.roughness;
    var alpha = (0, _ShaderNode.pow2)(roughness); // UE4's roughness

    var halfDir = (0, _ShaderNode.normalize)((0, _ShaderNode.add)(lightDirection, _ShaderNode.positionViewDirection));
    var dotNL = (0, _ShaderNode.saturate)((0, _ShaderNode.dot)(_ShaderNode.transformedNormalView, lightDirection));
    var dotNV = (0, _ShaderNode.saturate)((0, _ShaderNode.dot)(_ShaderNode.transformedNormalView, _ShaderNode.positionViewDirection));
    var dotNH = (0, _ShaderNode.saturate)((0, _ShaderNode.dot)(_ShaderNode.transformedNormalView, halfDir));
    var dotVH = (0, _ShaderNode.saturate)((0, _ShaderNode.dot)(_ShaderNode.positionViewDirection, halfDir));
    var F = F_Schlick({
      f0: f0,
      f90: f90,
      dotVH: dotVH
    });
    var V = V_GGX_SmithCorrelated({
      alpha: alpha,
      dotNL: dotNL,
      dotNV: dotNV
    });
    var D = D_GGX({
      alpha: alpha,
      dotNH: dotNH
    });
    return (0, _ShaderNode.mul)(F, (0, _ShaderNode.mul)(V, D));
  }); // validated

  _exports.BRDF_Specular_GGX = BRDF_Specular_GGX;
  var RE_Direct_Physical = new _ShaderNode.ShaderNode(function (inputs) {
    var lightDirection = inputs.lightDirection,
        lightColor = inputs.lightColor,
        directDiffuse = inputs.directDiffuse,
        directSpecular = inputs.directSpecular;
    var dotNL = (0, _ShaderNode.saturate)((0, _ShaderNode.dot)(_ShaderNode.transformedNormalView, lightDirection));
    var irradiance = (0, _ShaderNode.mul)(dotNL, lightColor);
    irradiance = (0, _ShaderNode.mul)(irradiance, _ShaderNode.PI); // punctual light

    (0, _ShaderNode.addTo)(directDiffuse, (0, _ShaderNode.mul)(irradiance, BRDF_Lambert({
      diffuseColor: _ShaderNode.diffuseColor
    })));
    (0, _ShaderNode.addTo)(directSpecular, (0, _ShaderNode.mul)(irradiance, BRDF_Specular_GGX({
      lightDirection: lightDirection,
      f0: _ShaderNode.specularColor,
      f90: 1,
      roughness: _ShaderNode.roughness
    })));
  });
  _exports.RE_Direct_Physical = RE_Direct_Physical;
  var PhysicalLightingModel = new _ShaderNode.ShaderNode(function (inputs
  /*, builder*/
  ) {
    // PHYSICALLY_CORRECT_LIGHTS <-> builder.renderer.physicallyCorrectLights === true
    RE_Direct_Physical(inputs);
  });
  _exports.PhysicalLightingModel = PhysicalLightingModel;
});