/**
* @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
*/
import {
BackSide,
BoxBufferGeometry,
Mesh,
ShaderMaterial,
UniformsUtils,
Vector3
} from "../../../build/three.module.js";
var Sky = function () {
var shader = Sky.SkyShader;
var material = new ShaderMaterial( {
fragmentShader: shader.fragmentShader,
vertexShader: shader.vertexShader,
uniforms: UniformsUtils.clone( shader.uniforms ),
side: BackSide
} );
Mesh.call( this, new BoxBufferGeometry( 1, 1, 1 ), material );
};
Sky.prototype = Object.create( Mesh.prototype );
Sky.SkyShader = {
uniforms: {
"luminance": { value: 1 },
"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: [
'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;',
'}'
].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;',
'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 );',
'}',
// 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 = vec4( retColor, 1.0 );',
'}'
].join( '\n' )
};
export { Sky };
