/** * @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;", // wavelength of used primaries, according to preetham "const vec3 lambda = vec3( 680E-9, 550E-9, 450E-9 );", // this pre-calcuation replaces older TotalRayleigh(vec3 lambda) function: // (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)) "const vec3 totalRayleigh = vec3( 5.804542996261093E-6, 1.3562911419845635E-5, 3.0265902468824876E-5 );", // mie stuff // K coefficient for the primaries "const float v = 4.0;", "const vec3 K = vec3( 0.686, 0.678, 0.666 );", // MieConst = pi * pow( ( 2.0 * pi ) / lambda, vec3( v - 2.0 ) ) * K "const vec3 MieConst = vec3( 1.8399918514433978E14, 2.7798023919660528E14, 4.0790479543861094E14 );", // earth shadow hack // cutoffAngle = pi / 1.95; "const float cutoffAngle = 1.6110731556870734;", "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( float T )", "{", "float c = ( 0.2 * T ) * 10E-18;", "return 0.434 * c * MieConst;", "}", "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 = totalRayleigh * rayleighCoefficient;", // mie coefficients "vBetaM = totalMie( 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, 0.0, 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 );", // 66 arc seconds -> degrees, and the cosine of that "const float sunAngularDiameterCos = 0.999956676946448443553574619906976478926848692873900859324;", // 3.0 / ( 16.0 * pi ) "const float THREE_OVER_SIXTEENPI = 0.05968310365946075;", // 1.0 / ( 4.0 * pi ) "const float ONE_OVER_FOURPI = 0.07957747154594767;", "float rayleighPhase( float cosTheta )", "{", "return THREE_OVER_SIXTEENPI * ( 1.0 + pow( cosTheta, 2.0 ) );", "}", "float hgPhase( float cosTheta, float g )", "{", "float g2 = pow( g, 2.0 );", "float inverse = 1.0 / pow( 1.0 - 2.0 * g * cosTheta + g2, 1.5 );", "return ONE_OVER_FOURPI * ( ( 1.0 - g2 ) * inverse );", "}", // 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 inverse = 1.0 / ( cos( zenithAngle ) + 0.15 * pow( 93.885 - ( ( zenithAngle * 180.0 ) / pi ), -1.253 ) );", "float sR = rayleighZenithLength * inverse;", "float sM = mieZenithLength * inverse;", // 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 = 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.SphereBufferGeometry( 450000, 32, 15 ); var skyMesh = new THREE.Mesh( skyGeo, skyMat ); // Expose variables this.mesh = skyMesh; this.uniforms = skyUniforms; };