/** * @author zz85 / https://github.com/zz85 * * Based on "A Practical Analytic Model for Daylight" * aka The Preetham Model, the de facto standard analytic skydome model * http://www.cs.utah.edu/~shirley/papers/sunsky/sunsky.pdf * * First implemented by Simon Wallner * http://www.simonwallner.at/projects/atmospheric-scattering * * Improved by Martin Upitis * http://blenderartists.org/forum/showthread.php?245954-preethams-sky-impementation-HDR * * Three.js integration by zz85 http://twitter.com/blurspline */ THREE.ShaderLib['sky'] = { uniforms: { luminance: { type: "f", value:1 }, turbidity: { type: "f", value:2 }, reileigh: { type: "f", value:1 }, mieCoefficient: { type: "f", value:0.005 }, mieDirectionalG: { type: "f", value:0.8 }, sunPosition: { type: "v3", value: new THREE.Vector3() } }, vertexShader: [ "varying vec3 vWorldPosition;", "void main() {", "vec4 worldPosition = modelMatrix * vec4( position, 1.0 );", "vWorldPosition = worldPosition.xyz;", "gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );", "}", ].join("\n"), fragmentShader: [ "uniform sampler2D skySampler;", "uniform vec3 sunPosition;", "varying vec3 vWorldPosition;", "vec3 cameraPos = vec3(0., 0., 0.);", "// uniform sampler2D sDiffuse;", "// const float turbidity = 10.0; //", "// const float reileigh = 2.; //", "// const float luminance = 1.0; //", "// const float mieCoefficient = 0.005;", "// const float mieDirectionalG = 0.8;", "uniform float luminance;", "uniform float turbidity;", "uniform float reileigh;", "uniform float mieCoefficient;", "uniform float mieDirectionalG;", "vec3 sunDirection = normalize(sunPosition);", "float reileighCoefficient = reileigh;", "// constants for atmospheric scattering", "const float e = 2.71828182845904523536028747135266249775724709369995957;", "const float pi = 3.141592653589793238462643383279502884197169;", "const float n = 1.0003; // refractive index of air", "const float N = 2.545E25; // number of molecules per unit volume for air at", "// 288.15K and 1013mb (sea level -45 celsius)", "const float pn = 0.035; // depolatization factor for standard air", "// wavelength of used primaries, according to preetham", "const vec3 lambda = vec3(680E-9, 550E-9, 450E-9);", "// mie stuff", "// K coefficient for the primaries", "const vec3 K = vec3(0.686, 0.678, 0.666);", "const float v = 4.0;", "// optical length at zenith for molecules", "const float rayleighZenithLength = 8.4E3;", "const float mieZenithLength = 1.25E3;", "const vec3 up = vec3(0.0, 1.0, 0.0);", "const float EE = 1000.0;", "const float sunAngularDiameterCos = 0.999956676946448443553574619906976478926848692873900859324;", "// 66 arc seconds -> degrees, and the cosine of that", "// earth shadow hack", "const float cutoffAngle = pi/1.95;", "const float steepness = 1.5;", "vec3 totalRayleigh(vec3 lambda)", "{", "return (8.0 * pow(pi, 3.0) * pow(pow(n, 2.0) - 1.0, 2.0) * (6.0 + 3.0 * pn)) / (3.0 * N * pow(lambda, vec3(4.0)) * (6.0 - 7.0 * pn));", "}", // see http://blenderartists.org/forum/showthread.php?321110-Shaders-and-Skybox-madness "// A simplied version of the total Reayleigh scattering to works on browsers that use ANGLE", "vec3 simplifiedRayleigh()", "{", "return 0.0005 / vec3(94, 40, 18);", // return 0.00054532832366 / (3.0 * 2.545E25 * pow(vec3(680E-9, 550E-9, 450E-9), vec3(4.0)) * 6.245); "}", "float rayleighPhase(float cosTheta)", "{ ", "return (3.0 / (16.0*pi)) * (1.0 + pow(cosTheta, 2.0));", "// return (1.0 / (3.0*pi)) * (1.0 + pow(cosTheta, 2.0));", "// return (3.0 / 4.0) * (1.0 + pow(cosTheta, 2.0));", "}", "vec3 totalMie(vec3 lambda, vec3 K, float T)", "{", "float c = (0.2 * T ) * 10E-18;", "return 0.434 * c * pi * pow((2.0 * pi) / lambda, vec3(v - 2.0)) * K;", "}", "float hgPhase(float cosTheta, float g)", "{", "return (1.0 / (4.0*pi)) * ((1.0 - pow(g, 2.0)) / pow(1.0 - 2.0*g*cosTheta + pow(g, 2.0), 1.5));", "}", "float sunIntensity(float zenithAngleCos)", "{", "return EE * max(0.0, 1.0 - exp(-((cutoffAngle - acos(zenithAngleCos))/steepness)));", "}", "// float logLuminance(vec3 c)", "// {", "// return log(c.r * 0.2126 + c.g * 0.7152 + c.b * 0.0722);", "// }", "// Filmic ToneMapping http://filmicgames.com/archives/75", "float A = 0.15;", "float B = 0.50;", "float C = 0.10;", "float D = 0.20;", "float E = 0.02;", "float F = 0.30;", "float W = 1000.0;", "vec3 Uncharted2Tonemap(vec3 x)", "{", "return ((x*(A*x+C*B)+D*E)/(x*(A*x+B)+D*F))-E/F;", "}", "void main() ", "{", "float sunfade = 1.0-clamp(1.0-exp((sunPosition.y/450000.0)),0.0,1.0);", "// luminance = 1.0 ;// vWorldPosition.y / 450000. + 0.5; //sunPosition.y / 450000. * 1. + 0.5;", "// gl_FragColor = vec4(sunfade, sunfade, sunfade, 1.0);", "reileighCoefficient = reileighCoefficient - (1.0* (1.0-sunfade));", "float sunE = sunIntensity(dot(sunDirection, up));", "// extinction (absorbtion + out scattering) ", "// rayleigh coefficients", // "vec3 betaR = totalRayleigh(lambda) * reileighCoefficient;", "vec3 betaR = simplifiedRayleigh() * reileighCoefficient;", "// mie coefficients", "vec3 betaM = totalMie(lambda, K, turbidity) * mieCoefficient;", "// optical length", "// cutoff angle at 90 to avoid singularity in next formula.", "float zenithAngle = acos(max(0.0, dot(up, normalize(vWorldPosition - cameraPos))));", "float sR = rayleighZenithLength / (cos(zenithAngle) + 0.15 * pow(93.885 - ((zenithAngle * 180.0) / pi), -1.253));", "float sM = mieZenithLength / (cos(zenithAngle) + 0.15 * pow(93.885 - ((zenithAngle * 180.0) / pi), -1.253));", "// combined extinction factor ", "vec3 Fex = exp(-(betaR * sR + betaM * sM));", "// in scattering", "float cosTheta = dot(normalize(vWorldPosition - cameraPos), sunDirection);", "float rPhase = rayleighPhase(cosTheta*0.5+0.5);", "vec3 betaRTheta = betaR * rPhase;", "float mPhase = hgPhase(cosTheta, mieDirectionalG);", "vec3 betaMTheta = betaM * mPhase;", "vec3 Lin = pow(sunE * ((betaRTheta + betaMTheta) / (betaR + betaM)) * (1.0 - Fex),vec3(1.5));", "Lin *= mix(vec3(1.0),pow(sunE * ((betaRTheta + betaMTheta) / (betaR + betaM)) * Fex,vec3(1.0/2.0)),clamp(pow(1.0-dot(up, sunDirection),5.0),0.0,1.0));", "//nightsky", "vec3 direction = normalize(vWorldPosition - cameraPos);", "float theta = acos(direction.y); // elevation --> y-axis, [-pi/2, pi/2]", "float phi = atan(direction.z, direction.x); // azimuth --> x-axis [-pi/2, pi/2]", "vec2 uv = vec2(phi, theta) / vec2(2.0*pi, pi) + vec2(0.5, 0.0);", "// vec3 L0 = texture2D(skySampler, uv).rgb+0.1 * Fex;", "vec3 L0 = vec3(0.1) * Fex;", "// composition + solar disc", "//if (cosTheta > sunAngularDiameterCos)", "float sundisk = smoothstep(sunAngularDiameterCos,sunAngularDiameterCos+0.00002,cosTheta);", "// if (normalize(vWorldPosition - cameraPos).y>0.0)", "L0 += (sunE * 19000.0 * Fex)*sundisk;", "vec3 whiteScale = 1.0/Uncharted2Tonemap(vec3(W));", "vec3 texColor = (Lin+L0); ", "texColor *= 0.04 ;", "texColor += vec3(0.0,0.001,0.0025)*0.3;", "float g_fMaxLuminance = 1.0;", "float fLumScaled = 0.1 / luminance; ", "float fLumCompressed = (fLumScaled * (1.0 + (fLumScaled / (g_fMaxLuminance * g_fMaxLuminance)))) / (1.0 + fLumScaled); ", "float ExposureBias = fLumCompressed;", "vec3 curr = Uncharted2Tonemap((log2(2.0/pow(luminance,4.0)))*texColor);", "vec3 color = curr*whiteScale;", "vec3 retColor = pow(color,vec3(1.0/(1.2+(1.2*sunfade))));", "gl_FragColor.rgb = retColor;", "gl_FragColor.a = 1.0;", "}", ].join("\n") }; THREE.Sky = function () { var skyShader = THREE.ShaderLib[ "sky" ]; var skyUniforms = THREE.UniformsUtils.clone( skyShader.uniforms ); var skyMat = new THREE.ShaderMaterial( { fragmentShader: skyShader.fragmentShader, vertexShader: skyShader.vertexShader, uniforms: skyUniforms, side: THREE.BackSide } ); var skyGeo = new THREE.SphereGeometry( 450000, 32, 15 ); var skyMesh = new THREE.Mesh( skyGeo, skyMat ); // Expose variables this.mesh = skyMesh; this.uniforms = skyUniforms; };