/** * @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: { value: 1 }, turbidity: { value: 2 }, rayleigh: { value: 1 }, mieCoefficient: { value: 0.005 }, mieDirectionalG: { value: 0.8 }, sunPosition: { value: new THREE.Vector3() } }, vertexShader: [ "uniform vec3 sunPosition;", "uniform float rayleigh;", "uniform float turbidity;", "uniform float mieCoefficient;", "varying vec3 vWorldPosition;", "varying vec3 vSunDirection;", "varying float vSunfade;", "varying vec3 vBetaR;", "varying vec3 vBetaM;", "varying float vSunE;", "const vec3 up = vec3(0.0, 1.0, 0.0);", // constants for atmospheric scattering "const float e = 2.71828182845904523536028747135266249775724709369995957;", "const float pi = 3.141592653589793238462643383279502884197169;", // mie stuff // K coefficient for the primaries "const float v = 4.0;", "const vec3 K = vec3(0.686, 0.678, 0.666);", // 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 "const vec3 simplifiedRayleigh = 0.0005 / vec3(94, 40, 18);", // wavelength of used primaries, according to preetham "const vec3 lambda = vec3(680E-9, 550E-9, 450E-9);", // earth shadow hack "const float cutoffAngle = pi/1.95;", "const float steepness = 1.5;", "const float EE = 1000.0;", "float sunIntensity(float zenithAngleCos)", "{", "zenithAngleCos = clamp(zenithAngleCos, -1.0, 1.0);", "return EE * max(0.0, 1.0 - pow(e, -((cutoffAngle - acos(zenithAngleCos))/steepness)));", "}", "vec3 totalMie(vec3 lambda, float T)", "{", "float c = (0.2 * T ) * 10E-18;", "return 0.434 * c * pi * pow((2.0 * pi) / lambda, vec3(v - 2.0)) * K;", "}", "void main() {", "vec4 worldPosition = modelMatrix * vec4( position, 1.0 );", "vWorldPosition = worldPosition.xyz;", "gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );", "vSunDirection = normalize(sunPosition);", "vSunE = sunIntensity(dot(vSunDirection, up));", "vSunfade = 1.0-clamp(1.0-exp((sunPosition.y/450000.0)),0.0,1.0);", "float rayleighCoefficient = rayleigh - (1.0 * (1.0-vSunfade));", // extinction (absorbtion + out scattering) // rayleigh coefficients "vBetaR = simplifiedRayleigh * rayleighCoefficient;", // mie coefficients "vBetaM = totalMie(lambda, turbidity) * mieCoefficient;", "}" ].join( "\n" ), fragmentShader: [ "varying vec3 vWorldPosition;", "varying vec3 vSunDirection;", "varying float vSunfade;", "varying vec3 vBetaR;", "varying vec3 vBetaM;", "varying float vSunE;", "uniform float luminance;", "uniform float mieDirectionalG;", "const vec3 cameraPos = vec3(0., 0., 0.);", // constants for atmospheric scattering "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) // 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 sunAngularDiameterCos = 0.999956676946448443553574619906976478926848692873900859324;", // 66 arc seconds -> degrees, and the cosine of that "float rayleighPhase(float cosTheta)", "{", "return (3.0 / (16.0*pi)) * (1.0 + pow(cosTheta, 2.0));", "}", "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));", "}", // Filmic ToneMapping http://filmicgames.com/archives/75 "const float A = 0.15;", "const float B = 0.50;", "const float C = 0.10;", "const float D = 0.20;", "const float E = 0.02;", "const float F = 0.30;", "const float whiteScale = 1.0748724675633854;", // 1.0 / Uncharted2Tonemap(1000.0) "vec3 Uncharted2Tonemap(vec3 x)", "{", "return ((x*(A*x+C*B)+D*E)/(x*(A*x+B)+D*F))-E/F;", "}", "void main() ", "{", // 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(-(vBetaR * sR + vBetaM * sM));", // in scattering "float cosTheta = dot(normalize(vWorldPosition - cameraPos), vSunDirection);", "float rPhase = rayleighPhase(cosTheta*0.5+0.5);", "vec3 betaRTheta = vBetaR * rPhase;", "float mPhase = hgPhase(cosTheta, mieDirectionalG);", "vec3 betaMTheta = vBetaM * mPhase;", "vec3 Lin = pow(vSunE * ((betaRTheta + betaMTheta) / (vBetaR + vBetaM)) * (1.0 - Fex),vec3(1.5));", "Lin *= mix(vec3(1.0),pow(vSunE * ((betaRTheta + betaMTheta) / (vBetaR + vBetaM)) * Fex,vec3(1.0/2.0)),clamp(pow(1.0-dot(up, vSunDirection),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 = vec3(0.1) * Fex;", // composition + solar disc "float sundisk = smoothstep(sunAngularDiameterCos,sunAngularDiameterCos+0.00002,cosTheta);", "L0 += (vSunE * 19000.0 * Fex)*sundisk;", "vec3 texColor = (Lin+L0) * 0.04 + vec3(0.0, 0.0003, 0.00075);", "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*vSunfade))));", "gl_FragColor.rgb = retColor;", "gl_FragColor.a = 1.0;", "}" ].join( "\n" ) }; THREE.Sky = function () { var skyShader = THREE.ShaderLib[ "sky" ]; var skyUniforms = Object.assign( {}, skyShader.uniforms ); var skyMat = new THREE.ShaderMaterial( { fragmentShader: skyShader.fragmentShader, vertexShader: skyShader.vertexShader, uniforms: skyUniforms, side: THREE.BackSide } ); var skyGeo = new THREE.SphereBufferGeometry( 450000, 32, 15 ); var skyMesh = new THREE.Mesh( skyGeo, skyMat ); // Expose variables this.mesh = skyMesh; this.uniforms = skyUniforms; };