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- import {
- BackSide,
- BoxGeometry,
- Mesh,
- NodeMaterial,
- Vector3
- } from 'three';
- import { float, Fn, vec3, acos, add, mul, clamp, cos, dot, exp, max, mix, modelViewProjection, normalize, positionWorld, pow, smoothstep, sub, varying, varyingProperty, vec4, uniform, cameraPosition } from 'three/tsl';
- /**
- * 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 SkyMesh extends Mesh {
- constructor() {
- const material = new NodeMaterial();
- super( new BoxGeometry( 1, 1, 1 ), material );
- this.turbidity = uniform( 2 );
- this.rayleigh = uniform( 1 );
- this.mieCoefficient = uniform( 0.005 );
- this.mieDirectionalG = uniform( 0.8 );
- this.sunPosition = uniform( new Vector3() );
- this.upUniform = uniform( new Vector3( 0, 1, 0 ) );
- this.isSky = true;
- const vertexNode = /*@__PURE__*/ Fn( () => {
- // constants for atmospheric scattering
- const e = float( 2.71828182845904523536028747135266249775724709369995957 );
- // const pi = float( 3.141592653589793238462643383279502884197169 );
- // wavelength of used primaries, according to preetham
- // const 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 totalRayleigh = vec3( 5.804542996261093E-6, 1.3562911419845635E-5, 3.0265902468824876E-5 );
- // mie stuff
- // K coefficient for the primaries
- // const v = float( 4.0 );
- // const K = vec3( 0.686, 0.678, 0.666 );
- // MieConst = pi * pow( ( 2.0 * pi ) / lambda, vec3( v - 2.0 ) ) * K
- const MieConst = vec3( 1.8399918514433978E14, 2.7798023919660528E14, 4.0790479543861094E14 );
- // earth shadow hack
- // cutoffAngle = pi / 1.95;
- const cutoffAngle = float( 1.6110731556870734 );
- const steepness = float( 1.5 );
- const EE = float( 1000.0 );
- // varying sun position
- const vSunDirection = normalize( this.sunPosition );
- varyingProperty( 'vec3', 'vSunDirection' ).assign( vSunDirection );
- // varying sun intensity
- const angle = dot( vSunDirection, this.upUniform );
- const zenithAngleCos = clamp( angle, - 1, 1 );
- const sunIntensity = EE.mul( max( 0.0, float( 1.0 ).sub( pow( e, cutoffAngle.sub( acos( zenithAngleCos ) ).div( steepness ).negate() ) ) ) );
- varyingProperty( 'float', 'vSunE' ).assign( sunIntensity );
- // varying sun fade
- const vSunfade = float( 1.0 ).sub( clamp( float( 1.0 ).sub( exp( this.sunPosition.y.div( 450000.0 ) ) ), 0, 1 ) );
- varyingProperty( 'float', 'vSunfade' ).assign( vSunfade );
- // varying vBetaR
- const rayleighCoefficient = this.rayleigh.sub( float( 1.0 ).mul( float( 1.0 ).sub( vSunfade ) ) );
- // extinction (absorbtion + out scattering)
- // rayleigh coefficients
- varyingProperty( 'vec3', 'vBetaR' ).assign( totalRayleigh.mul( rayleighCoefficient ) );
- // varying vBetaM
- const c = float( 0.2 ).mul( this.turbidity ).mul( 10E-18 );
- const totalMie = float( 0.434 ).mul( c ).mul( MieConst );
- varyingProperty( 'vec3', 'vBetaM' ).assign( totalMie.mul( this.mieCoefficient ) );
- // position
- const position = modelViewProjection();
- position.z.assign( position.w ); // set z to camera.far
- return position;
- } )();
- const fragmentNode = /*@__PURE__*/ Fn( () => {
- const vSunDirection = varying( vec3(), 'vSunDirection' );
- const vSunE = varying( float(), 'vSunE' );
- const vSunfade = varying( float(), 'vSunfade' );
- const vBetaR = varying( vec3(), 'vBetaR' );
- const vBetaM = varying( vec3(), 'vBetaM' );
- // constants for atmospheric scattering
- const pi = float( 3.141592653589793238462643383279502884197169 );
- // optical length at zenith for molecules
- const rayleighZenithLength = float( 8.4E3 );
- const mieZenithLength = float( 1.25E3 );
- // 66 arc seconds -> degrees, and the cosine of that
- const sunAngularDiameterCos = float( 0.999956676946448443553574619906976478926848692873900859324 );
- // 3.0 / ( 16.0 * pi )
- const THREE_OVER_SIXTEENPI = float( 0.05968310365946075 );
- // 1.0 / ( 4.0 * pi )
- const ONE_OVER_FOURPI = float( 0.07957747154594767 );
- //
- const direction = normalize( positionWorld.sub( cameraPosition ) );
- // optical length
- // cutoff angle at 90 to avoid singularity in next formula.
- const zenithAngle = acos( max( 0.0, dot( this.upUniform, direction ) ) );
- const inverse = float( 1.0 ).div( cos( zenithAngle ).add( float( 0.15 ).mul( pow( float( 93.885 ).sub( zenithAngle.mul( 180.0 ).div( pi ) ), - 1.253 ) ) ) );
- const sR = rayleighZenithLength.mul( inverse );
- const sM = mieZenithLength.mul( inverse );
- // combined extinction factor
- const Fex = exp( mul( vBetaR, sR ).add( mul( vBetaM, sM ) ).negate() );
- // in scattering
- const cosTheta = dot( direction, vSunDirection );
- // betaRTheta
- const c = cosTheta.mul( 0.5 ).add( 0.5 );
- const rPhase = THREE_OVER_SIXTEENPI.mul( float( 1.0 ).add( pow( c, 2.0 ) ) );
- const betaRTheta = vBetaR.mul( rPhase );
- // betaMTheta
- const g2 = pow( this.mieDirectionalG, 2.0 );
- const inv = float( 1.0 ).div( pow( float( 1.0 ).sub( float( 2.0 ).mul( this.mieDirectionalG ).mul( cosTheta ) ).add( g2 ), 1.5 ) );
- const mPhase = ONE_OVER_FOURPI.mul( float( 1.0 ).sub( g2 ) ).mul( inv );
- const betaMTheta = vBetaM.mul( mPhase );
- const Lin = pow( vSunE.mul( add( betaRTheta, betaMTheta ).div( add( vBetaR, vBetaM ) ) ).mul( sub( 1.0, Fex ) ), vec3( 1.5 ) );
- Lin.mulAssign( mix( vec3( 1.0 ), pow( vSunE.mul( add( betaRTheta, betaMTheta ).div( add( vBetaR, vBetaM ) ) ).mul( Fex ), vec3( 1.0 / 2.0 ) ), clamp( pow( sub( 1.0, dot( this.upUniform, vSunDirection ) ), 5.0 ), 0.0, 1.0 ) ) );
- // nightsky
- const L0 = vec3( 0.1 ).mul( Fex );
- // composition + solar disc
- const sundisk = smoothstep( sunAngularDiameterCos, sunAngularDiameterCos.add( 0.00002 ), cosTheta );
- L0.addAssign( vSunE.mul( 19000.0 ).mul( Fex ).mul( sundisk ) );
- const texColor = add( Lin, L0 ).mul( 0.04 ).add( vec3( 0.0, 0.0003, 0.00075 ) );
- const retColor = pow( texColor, vec3( float( 1.0 ).div( float( 1.2 ).add( vSunfade.mul( 1.2 ) ) ) ) );
- return vec4( retColor, 1.0 );
- } )();
- material.side = BackSide;
- material.depthWrite = false;
- material.vertexNode = vertexNode;
- material.fragmentNode = fragmentNode;
- }
- }
- export { SkyMesh };
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