import { BackSide, BoxGeometry, Mesh, ShaderMaterial, UniformsUtils, Vector3 } from 'three'; /** * Based on "A Practical Analytic Model for Daylight" * aka The Preetham Model, the de facto standard analytic skydome model * https://www.researchgate.net/publication/220720443_A_Practical_Analytic_Model_for_Daylight * * First implemented by Simon Wallner * http://simonwallner.at/project/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 */ class Sky extends Mesh { constructor() { const shader = Sky.SkyShader; const material = new ShaderMaterial( { name: 'SkyShader', fragmentShader: shader.fragmentShader, vertexShader: shader.vertexShader, uniforms: UniformsUtils.clone( shader.uniforms ), side: BackSide, depthWrite: false } ); super( new BoxGeometry( 1, 1, 1 ), material ); this.isSky = true; } } Sky.SkyShader = { uniforms: { 'turbidity': { value: 2 }, 'rayleigh': { value: 1 }, 'mieCoefficient': { value: 0.005 }, 'mieDirectionalG': { value: 0.8 }, 'sunPosition': { value: new Vector3() }, 'up': { value: new Vector3( 0, 1, 0 ) } }, vertexShader: /* glsl */` uniform vec3 sunPosition; uniform float rayleigh; uniform float turbidity; uniform float mieCoefficient; uniform vec3 up; varying vec3 vWorldPosition; varying vec3 vSunDirection; varying float vSunfade; varying vec3 vBetaR; varying vec3 vBetaM; varying float vSunE; // 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 ); gl_Position.z = gl_Position.w; // set z to camera.far 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; }`, fragmentShader: /* glsl */` varying vec3 vWorldPosition; varying vec3 vSunDirection; varying float vSunfade; varying vec3 vBetaR; varying vec3 vBetaM; varying float vSunE; uniform float mieDirectionalG; uniform vec3 up; 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; // 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 ); } void main() { vec3 direction = normalize( vWorldPosition - cameraPos ); // optical length // cutoff angle at 90 to avoid singularity in next formula. float zenithAngle = acos( max( 0.0, dot( up, direction ) ) ); 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( direction, 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 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 retColor = pow( texColor, vec3( 1.0 / ( 1.2 + ( 1.2 * vSunfade ) ) ) ); gl_FragColor = vec4( retColor, 1.0 ); #include #include }` }; export { Sky };