/**
 * @author yomboprime https://github.com/yomboprime
 *
 * @fileoverview LightningStrike object for creating lightning strikes and voltaic arcs.
 *
 *
 * Usage
 *
 * var myRay = new LightningStrike( paramsObject );
 * var myRayMesh = new THREE.Mesh( myRay, myMaterial );
 * scene.add( myRayMesh );
 * ...
 * myRay.update( currentTime );
 *
 * The "currentTime" can vary its rate, go forwards, backwards or even jump, but it cannot be negative.
 *
 * You should normally leave the ray position to (0, 0, 0). You should control it by changing the sourceOffset and destOffset parameters.
 *
 *
 * LightningStrike parameters
 *
 * The paramsObject can contain any of the following parameters.
 *
 * Legend:
 * 'LightningStrike' (also called 'ray'): An independent voltaic arc with its ramifications and defined with a set of parameters.
 * 'Subray': A ramification of the ray. It is not a LightningStrike object.
 * 'Segment': A linear segment piece of a subray.
 * 'Leaf segment': A ray segment which cannot be smaller.
 *
 *
 * The following parameters can be changed any time and if they vary smoothly, the ray form will also change smoothly:
 *
 * @param {Vector3} sourceOffset The point where the ray starts.
 *
 * @param {Vector3} destOffset The point where the ray ends.
 *
 * @param {double} timeScale The rate at wich the ray form changes in time. Default: 1
 *
 * @param {double} roughness From 0 to 1. The higher the value, the more wrinkled is the ray. Default: 0.9
 *
 * @param {double} straightness From 0 to 1. The higher the value, the more straight will be a subray path. Default: 0.7
 *
 * @param {Vector3} up0 Ray 'up' direction at the ray starting point. Must be normalized. It should be perpendicular to the ray forward direction but it doesn't matter much.
 *
 * @param {Vector3} up1 Like the up0 parameter but at the end of the ray. Must be normalized.
 *
 * @param {double} radius0 Radius of the main ray trunk at the start point. Default: 1
 *
 * @param {double} radius1 Radius of the main ray trunk at the end point. Default: 1
 *
 * @param {double} radius0Factor The radius0 of a subray is this factor times the radius0 of its parent subray. Default: 0.5
 *
 * @param {double} radius1Factor The radius1 of a subray is this factor times the radius1 of its parent subray. Default: 0.2
 *
 * @param {minRadius} Minimum value a subray radius0 or radius1 can get. Default: 0.1
 *
 *
 * The following parameters should not be changed after lightning creation. They can be changed but the ray will change its form abruptly:
 *
 * @param {boolean} isEternal If true the ray never extinguishes. Otherwise its life is controlled by the 'birthTime' and 'deathTime' parameters. Default: true if any of those two parameters is undefined.
 *
 * @param {double} birthTime The time at which the ray starts its life and begins propagating. Only if isEternal is false. Default: None.
 *
 * @param {double} deathTime The time at which the ray ends vanishing and its life. Only if isEternal is false. Default: None.
 *
 * @param {double} propagationTimeFactor From 0 to 1. Lifetime factor at which the ray ends propagating and enters the steady phase. For example, 0.1 means it is propagating 1/10 of its lifetime. Default: 0.1
 *
 * @param {double} vanishingTimeFactor From 0 to 1. Lifetime factor at which the ray ends the steady phase and begins vanishing. For example, 0.9 means it is vanishing 1/10 of its lifetime. Default: 0.9
 *
 * @param {double} subrayPeriod Subrays cycle periodically. This is their time period. Default: 4
 *
 * @param {double} subrayDutyCycle From 0 to 1. This is the fraction of time a subray is active. Default: 0.6
 *
 *
 * These parameters cannot change after lightning creation:
 *
 * @param {integer} maxIterations: Greater than 0. The number of ray's leaf segments is 2**maxIterations. Default: 9
 *
 * @param {boolean} isStatic Set to true only for rays which won't change over time and are not attached to moving objects (Rare case). It is used to set the vertex buffers non-dynamic. You can omit calling update() for these rays.
 *
 * @param {integer} ramification Greater than 0. Maximum number of child subrays a subray can have. Default: 5
 *
 * @param {integer} maxSubrayRecursion Greater than 0. Maximum level of recursion (subray descendant generations). Default: 3
 *
 * @param {double} recursionProbability From 0 to 1. The lower the value, the less chance each new generation of subrays has to generate new subrays. Default: 0.6
 *
 * @param {boolean} generateUVs If true, the ray geometry will have uv coordinates generated. u runs along the ray, and v across its perimeter. Default: false.
 *
 * @param {Object} randomGenerator Set here your random number generator which will seed the SimplexNoise and other decisions during ray tree creation.
 * It can be used to generate repeatable rays. For that, set also the noiseSeed parameter, and each ray created with that generator and seed pair will be identical in time.
 * The randomGenerator parameter should be an object with a random() function similar to Math.random, but seedable.
 * It must have also a getSeed() method, which returns the current seed, and a setSeed( seed ) method, which accepts as seed a fractional number from 0 to 1, as well as any other number.
 * The default value is an internal generator for some uses and Math.random for others (It is non-repeatable even if noiseSeed is supplied)
 *
 * @param {double} noiseSeed Seed used to make repeatable rays (see the randomGenerator)
 *
 * @param {function} onDecideSubrayCreation Set this to change the callback which decides subray creation. You can look at the default callback in the code (createDefaultSubrayCreationCallbacks)for more info.
 *
 * @param {function} onSubrayCreation This is another callback, more simple than the previous one. It can be used to adapt the form of subrays or other parameters once a subray has been created and initialized. It is used in the examples to adapt subrays to a sphere or to a plane.
 *
 *
*/

import {
	BufferGeometry,
	DynamicDrawUsage,
	Float32BufferAttribute,
	Math as _Math,
	Uint32BufferAttribute,
	Vector3
} from "../../../build/three.module.js";
import { SimplexNoise } from "../math/SimplexNoise.js";

var LightningStrike = function ( rayParameters ) {

	BufferGeometry.call( this );

	this.type = 'LightningStrike';

	// Set parameters, and set undefined parameters to default values
	rayParameters = rayParameters || {};
	this.init( LightningStrike.copyParameters( rayParameters, rayParameters ) );

	// Creates and populates the mesh
	this.createMesh();

};

LightningStrike.prototype = Object.create( BufferGeometry.prototype );

LightningStrike.prototype.constructor = LightningStrike;

LightningStrike.prototype.isLightningStrike = true;

// Ray states
LightningStrike.RAY_INITIALIZED = 0;
LightningStrike.RAY_UNBORN = 1;
LightningStrike.RAY_PROPAGATING = 2;
LightningStrike.RAY_STEADY = 3;
LightningStrike.RAY_VANISHING = 4;
LightningStrike.RAY_EXTINGUISHED = 5;

LightningStrike.COS30DEG = Math.cos( 30 * Math.PI / 180 );
LightningStrike.SIN30DEG = Math.sin( 30 * Math.PI / 180 );

LightningStrike.createRandomGenerator = function () {

	var numSeeds = 2053;
	var seeds = [];

	for ( var i = 0; i < numSeeds; i ++ ) {

		seeds.push( Math.random() );

	}

	var generator = {

		currentSeed: 0,

		random: function () {

			var value = seeds[ generator.currentSeed ];

			generator.currentSeed = ( generator.currentSeed + 1 ) % numSeeds;

			return value;

		},

		getSeed: function () {

			return generator.currentSeed / numSeeds;

		},

		setSeed: function ( seed ) {

			generator.currentSeed = Math.floor( seed * numSeeds ) % numSeeds;

		}

	};

	return generator;

};

LightningStrike.copyParameters = function ( dest, source ) {

	source = source || {};
	dest = dest || {};

	var vecCopy = function ( v ) {

		if ( source === dest ) {

			return v;

		} else {

			return v.clone();

		}

	};

	dest.sourceOffset = source.sourceOffset !== undefined ? vecCopy( source.sourceOffset ) : new Vector3( 0, 100, 0 ),
	dest.destOffset = source.destOffset !== undefined ? vecCopy( source.destOffset ) : new Vector3( 0, 0, 0 ),

	dest.timeScale = source.timeScale !== undefined ? source.timeScale : 1,
	dest.roughness = source.roughness !== undefined ? source.roughness : 0.9,
	dest.straightness = source.straightness !== undefined ? source.straightness : 0.7,

	dest.up0 = source.up0 !== undefined ? vecCopy( source.up0 ) : new Vector3( 0, 0, 1 );
	dest.up1 = source.up1 !== undefined ? vecCopy( source.up1 ) : new Vector3( 0, 0, 1 ),
	dest.radius0 = source.radius0 !== undefined ? source.radius0 : 1,
	dest.radius1 = source.radius1 !== undefined ? source.radius1 : 1,
	dest.radius0Factor = source.radius0Factor !== undefined ? source.radius0Factor : 0.5,
	dest.radius1Factor = source.radius1Factor !== undefined ? source.radius1Factor : 0.2,
	dest.minRadius = source.minRadius !== undefined ? source.minRadius : 0.2,

	// These parameters should not be changed after lightning creation. They can be changed but the ray will change its form abruptly:

	dest.isEternal = source.isEternal !== undefined ? source.isEternal : ( source.birthTime === undefined || source.deathTime === undefined ),
	dest.birthTime = source.birthTime,
	dest.deathTime = source.deathTime,
	dest.propagationTimeFactor = source.propagationTimeFactor !== undefined ? source.propagationTimeFactor : 0.1,
	dest.vanishingTimeFactor = source.vanishingTimeFactor !== undefined ? source.vanishingTimeFactor : 0.9,
	dest.subrayPeriod = source.subrayPeriod !== undefined ? source.subrayPeriod : 4,
	dest.subrayDutyCycle = source.subrayDutyCycle !== undefined ? source.subrayDutyCycle : 0.6;

	// These parameters cannot change after lightning creation:

	dest.maxIterations = source.maxIterations !== undefined ? source.maxIterations : 9;
	dest.isStatic = source.isStatic !== undefined ? source.isStatic : false;
	dest.ramification = source.ramification !== undefined ? source.ramification : 5;
	dest.maxSubrayRecursion = source.maxSubrayRecursion !== undefined ? source.maxSubrayRecursion : 3;
	dest.recursionProbability = source.recursionProbability !== undefined ? source.recursionProbability : 0.6;
	dest.generateUVs = source.generateUVs !== undefined ? source.generateUVs : false;
	dest.randomGenerator = source.randomGenerator,
	dest.noiseSeed = source.noiseSeed,
	dest.onDecideSubrayCreation = source.onDecideSubrayCreation,
	dest.onSubrayCreation = source.onSubrayCreation;

	return dest;

};

LightningStrike.prototype.update = function ( time ) {

	if ( this.isStatic ) return;

	if ( this.rayParameters.isEternal || ( this.rayParameters.birthTime <= time && time <= this.rayParameters.deathTime ) ) {

		this.updateMesh( time );

		if ( time < this.subrays[ 0 ].endPropagationTime ) {

			this.state = LightningStrike.RAY_PROPAGATING;

		} else if ( time > this.subrays[ 0 ].beginVanishingTime ) {

			this.state = LightningStrike.RAY_VANISHING;

		} else {

			this.state = LightningStrike.RAY_STEADY;

		}

		this.visible = true;

	} else {

		this.visible = false;

		if ( time < this.rayParameters.birthTime ) {

			this.state = LightningStrike.RAY_UNBORN;

		} else {

			this.state = LightningStrike.RAY_EXTINGUISHED;

		}

	}

};

LightningStrike.prototype.init = function ( rayParameters ) {

	// Init all the state from the parameters

	this.rayParameters = rayParameters;

	// These parameters cannot change after lightning creation:

	this.maxIterations = rayParameters.maxIterations !== undefined ? Math.floor( rayParameters.maxIterations ) : 9;
	rayParameters.maxIterations = this.maxIterations;
	this.isStatic = rayParameters.isStatic !== undefined ? rayParameters.isStatic : false;
	rayParameters.isStatic = this.isStatic;
	this.ramification = rayParameters.ramification !== undefined ? Math.floor( rayParameters.ramification ) : 5;
	rayParameters.ramification = this.ramification;
	this.maxSubrayRecursion = rayParameters.maxSubrayRecursion !== undefined ? Math.floor( rayParameters.maxSubrayRecursion ) : 3;
	rayParameters.maxSubrayRecursion = this.maxSubrayRecursion;
	this.recursionProbability = rayParameters.recursionProbability !== undefined ? rayParameters.recursionProbability : 0.6;
	rayParameters.recursionProbability = this.recursionProbability;
	this.generateUVs = rayParameters.generateUVs !== undefined ? rayParameters.generateUVs : false;
	rayParameters.generateUVs = this.generateUVs;

	// Random generator
	if ( rayParameters.randomGenerator !== undefined ) {

		this.randomGenerator = rayParameters.randomGenerator;
		this.seedGenerator = rayParameters.randomGenerator;

		if ( rayParameters.noiseSeed !== undefined ) {

			this.seedGenerator.setSeed( rayParameters.noiseSeed );

		}

	} else {

		this.randomGenerator = LightningStrike.createRandomGenerator();
		this.seedGenerator = Math;

	}

	// Ray creation callbacks
	if ( rayParameters.onDecideSubrayCreation !== undefined ) {

		this.onDecideSubrayCreation = rayParameters.onDecideSubrayCreation;

	} else {

		this.createDefaultSubrayCreationCallbacks();

		if ( rayParameters.onSubrayCreation !== undefined ) {

			this.onSubrayCreation = rayParameters.onSubrayCreation;

		}

	}

	// Internal state

	this.state = LightningStrike.RAY_INITIALIZED;

	this.maxSubrays = Math.ceil( 1 + Math.pow( this.ramification, Math.max( 0, this.maxSubrayRecursion - 1 ) ) );
	rayParameters.maxSubrays = this.maxSubrays;

	this.maxRaySegments = 2 * ( 1 << this.maxIterations );

	this.subrays = [];

	for ( var i = 0; i < this.maxSubrays; i ++ ) {

		this.subrays.push( this.createSubray() );

	}

	this.raySegments = [];

	for ( var i = 0; i < this.maxRaySegments; i ++ ) {

		this.raySegments.push( this.createSegment() );

	}

	this.time = 0;
	this.timeFraction = 0;
	this.currentSegmentCallback = null;
	this.currentCreateTriangleVertices = this.generateUVs ? this.createTriangleVerticesWithUVs : this.createTriangleVerticesWithoutUVs;
	this.numSubrays = 0;
	this.currentSubray = null;
	this.currentSegmentIndex = 0;
	this.isInitialSegment = false;
	this.subrayProbability = 0;

	this.currentVertex = 0;
	this.currentIndex = 0;
	this.currentCoordinate = 0;
	this.currentUVCoordinate = 0;
	this.vertices = null;
	this.uvs = null;
	this.indices = null;
	this.positionAttribute = null;
	this.uvsAttribute = null;

	this.simplexX = new SimplexNoise( this.seedGenerator );
	this.simplexY = new SimplexNoise( this.seedGenerator );
	this.simplexZ = new SimplexNoise( this.seedGenerator );

	// Temp vectors
	this.forwards = new Vector3();
	this.forwardsFill = new Vector3();
	this.side = new Vector3();
	this.down = new Vector3();
	this.middlePos = new Vector3();
	this.middleLinPos = new Vector3();
	this.newPos = new Vector3();
	this.vPos = new Vector3();
	this.cross1 = new Vector3();

};

LightningStrike.prototype.createMesh = function () {

	var maxDrawableSegmentsPerSubRay = 1 << this.maxIterations;

	var maxVerts = 3 * ( maxDrawableSegmentsPerSubRay + 1 ) * this.maxSubrays;
	var maxIndices = 18 * maxDrawableSegmentsPerSubRay * this.maxSubrays;

	this.vertices = new Float32Array( maxVerts * 3 );
	this.indices = new Uint32Array( maxIndices );
	if ( this.generateUVs ) {

		this.uvs = new Float32Array( maxVerts * 2 );

	}

	// Populate the mesh
	this.fillMesh( 0 );

	this.setIndex( new Uint32BufferAttribute( this.indices, 1 ) );

	this.positionAttribute = new Float32BufferAttribute( this.vertices, 3 );
	this.setAttribute( 'position', this.positionAttribute );

	if ( this.generateUVs ) {

		this.uvsAttribute = new Float32BufferAttribute( new Float32Array( this.uvs ), 2 );
		this.setAttribute( 'uv', this.uvsAttribute );

	}

	if ( ! this.isStatic ) {

		this.index.usage = DynamicDrawUsage;
		this.positionAttribute.usage = DynamicDrawUsage;
		if ( this.generateUVs ) {

			this.uvsAttribute.usage = DynamicDrawUsage;

		}

	}

	// Store buffers for later modification
	this.vertices = this.positionAttribute.array;
	this.indices = this.index.array;
	if ( this.generateUVs ) {

		this.uvs = this.uvsAttribute.array;

	}

};

LightningStrike.prototype.updateMesh = function ( time ) {

	this.fillMesh( time );

	this.drawRange.count = this.currentIndex;

	this.index.needsUpdate = true;

	this.positionAttribute.needsUpdate = true;

	if ( this.generateUVs ) {

		this.uvsAttribute.needsUpdate = true;

	}

};

LightningStrike.prototype.fillMesh = function ( time ) {

	var scope = this;

	this.currentVertex = 0;
	this.currentIndex = 0;
	this.currentCoordinate = 0;
	this.currentUVCoordinate = 0;

	this.fractalRay( time, function fillVertices( segment ) {

		var subray = scope.currentSubray;

		if ( time < subray.birthTime ) { //&& ( ! this.rayParameters.isEternal || scope.currentSubray.recursion > 0 ) ) {

			return;

		} else if ( this.rayParameters.isEternal && scope.currentSubray.recursion == 0 ) {

			// Eternal rays don't propagate nor vanish, but its subrays do

			scope.createPrism( segment );

			scope.onDecideSubrayCreation( segment, scope );

		} else if ( time < subray.endPropagationTime ) {

			if ( scope.timeFraction >= segment.fraction0 * subray.propagationTimeFactor ) {

				// Ray propagation has arrived to this segment

				scope.createPrism( segment );

				scope.onDecideSubrayCreation( segment, scope );

			}

		} else if ( time < subray.beginVanishingTime ) {

			// Ray is steady (nor propagating nor vanishing)

			scope.createPrism( segment );

			scope.onDecideSubrayCreation( segment, scope );

		} else {

			if ( scope.timeFraction <= subray.vanishingTimeFactor + segment.fraction1 * ( 1 - subray.vanishingTimeFactor ) ) {

				// Segment has not yet vanished

				scope.createPrism( segment );

			}

			scope.onDecideSubrayCreation( segment, scope );

		}

	} );

};

LightningStrike.prototype.addNewSubray = function ( /*rayParameters*/ ) {

	return this.subrays[ this.numSubrays ++ ];

};

LightningStrike.prototype.initSubray = function ( subray, rayParameters ) {

	subray.pos0.copy( rayParameters.sourceOffset );
	subray.pos1.copy( rayParameters.destOffset );
	subray.up0.copy( rayParameters.up0 );
	subray.up1.copy( rayParameters.up1 );
	subray.radius0 = rayParameters.radius0;
	subray.radius1 = rayParameters.radius1;
	subray.birthTime = rayParameters.birthTime;
	subray.deathTime = rayParameters.deathTime;
	subray.timeScale = rayParameters.timeScale;
	subray.roughness = rayParameters.roughness;
	subray.straightness = rayParameters.straightness;
	subray.propagationTimeFactor = rayParameters.propagationTimeFactor;
	subray.vanishingTimeFactor = rayParameters.vanishingTimeFactor;

	subray.maxIterations = this.maxIterations;
	subray.seed = rayParameters.noiseSeed !== undefined ? rayParameters.noiseSeed : 0;
	subray.recursion = 0;

};

LightningStrike.prototype.fractalRay = function ( time, segmentCallback ) {

	this.time = time;
	this.currentSegmentCallback = segmentCallback;
	this.numSubrays = 0;

	// Add the top level subray
	this.initSubray( this.addNewSubray(), this.rayParameters );

	// Process all subrays that are being generated until consuming all of them
	for ( var subrayIndex = 0; subrayIndex < this.numSubrays; subrayIndex ++ ) {

		var subray = this.subrays[ subrayIndex ];
		this.currentSubray = subray;

		this.randomGenerator.setSeed( subray.seed );

		subray.endPropagationTime = _Math.lerp( subray.birthTime, subray.deathTime, subray.propagationTimeFactor );
		subray.beginVanishingTime = _Math.lerp( subray.deathTime, subray.birthTime, 1 - subray.vanishingTimeFactor );

		var random1 = this.randomGenerator.random;
		subray.linPos0.set( random1(), random1(), random1() ).multiplyScalar( 1000 );
		subray.linPos1.set( random1(), random1(), random1() ).multiplyScalar( 1000 );

		this.timeFraction = ( time - subray.birthTime ) / ( subray.deathTime - subray.birthTime );

		this.currentSegmentIndex = 0;
		this.isInitialSegment = true;

		var segment = this.getNewSegment();
		segment.iteration = 0;
		segment.pos0.copy( subray.pos0 );
		segment.pos1.copy( subray.pos1 );
		segment.linPos0.copy( subray.linPos0 );
		segment.linPos1.copy( subray.linPos1 );
		segment.up0.copy( subray.up0 );
		segment.up1.copy( subray.up1 );
		segment.radius0 = subray.radius0;
		segment.radius1 = subray.radius1;
		segment.fraction0 = 0;
		segment.fraction1 = 1;
		segment.positionVariationFactor = 1 - subray.straightness;

		this.subrayProbability = this.ramification * Math.pow( this.recursionProbability, subray.recursion ) / ( 1 << subray.maxIterations );

		this.fractalRayRecursive( segment );

	}

	this.currentSegmentCallback = null;
	this.currentSubray = null;

};

LightningStrike.prototype.fractalRayRecursive = function ( segment ) {

	// Leave recursion condition
	if ( segment.iteration >= this.currentSubray.maxIterations ) {

		this.currentSegmentCallback( segment );

		return;

	}

	// Interpolation
	this.forwards.subVectors( segment.pos1, segment.pos0 );
	var lForwards = this.forwards.length();

	if ( lForwards < 0.000001 ) {

		this.forwards.set( 0, 0, 0.01 );
		lForwards = this.forwards.length();

	}

	var middleRadius = ( segment.radius0 + segment.radius1 ) * 0.5;
	var middleFraction = ( segment.fraction0 + segment.fraction1 ) * 0.5;

	var timeDimension = this.time * this.currentSubray.timeScale * Math.pow( 2, segment.iteration );

	this.middlePos.lerpVectors( segment.pos0, segment.pos1, 0.5 );
	this.middleLinPos.lerpVectors( segment.linPos0, segment.linPos1, 0.5 );
	var p = this.middleLinPos;

	// Noise
	this.newPos.set( this.simplexX.noise4d( p.x, p.y, p.z, timeDimension ),
		this.simplexY.noise4d( p.x, p.y, p.z, timeDimension ),
		this.simplexZ.noise4d( p.x, p.y, p.z, timeDimension ) );

	this.newPos.multiplyScalar( segment.positionVariationFactor * lForwards );
	this.newPos.add( this.middlePos );

	// Recursion

	var newSegment1 = this.getNewSegment();
	newSegment1.pos0.copy( segment.pos0 );
	newSegment1.pos1.copy( this.newPos );
	newSegment1.linPos0.copy( segment.linPos0 );
	newSegment1.linPos1.copy( this.middleLinPos );
	newSegment1.up0.copy( segment.up0 );
	newSegment1.up1.copy( segment.up1 );
	newSegment1.radius0 = segment.radius0;
	newSegment1.radius1 = middleRadius;
	newSegment1.fraction0 = segment.fraction0;
	newSegment1.fraction1 = middleFraction;
	newSegment1.positionVariationFactor = segment.positionVariationFactor * this.currentSubray.roughness;
	newSegment1.iteration = segment.iteration + 1;

	var newSegment2 = this.getNewSegment();
	newSegment2.pos0.copy( this.newPos );
	newSegment2.pos1.copy( segment.pos1 );
	newSegment2.linPos0.copy( this.middleLinPos );
	newSegment2.linPos1.copy( segment.linPos1 );
	this.cross1.crossVectors( segment.up0, this.forwards.normalize() );
	newSegment2.up0.crossVectors( this.forwards, this.cross1 ).normalize();
	newSegment2.up1.copy( segment.up1 );
	newSegment2.radius0 = middleRadius;
	newSegment2.radius1 = segment.radius1;
	newSegment2.fraction0 = middleFraction;
	newSegment2.fraction1 = segment.fraction1;
	newSegment2.positionVariationFactor = segment.positionVariationFactor * this.currentSubray.roughness;
	newSegment2.iteration = segment.iteration + 1;

	this.fractalRayRecursive( newSegment1 );

	this.fractalRayRecursive( newSegment2 );

};

LightningStrike.prototype.createPrism = function ( segment ) {

	// Creates one triangular prism and its vertices at the segment

	this.forwardsFill.subVectors( segment.pos1, segment.pos0 ).normalize();

	if ( this.isInitialSegment ) {

		this.currentCreateTriangleVertices( segment.pos0, segment.up0, this.forwardsFill, segment.radius0, 0 );

		this.isInitialSegment = false;

	}

	this.currentCreateTriangleVertices( segment.pos1, segment.up0, this.forwardsFill, segment.radius1, segment.fraction1 );

	this.createPrismFaces();

};

LightningStrike.prototype.createTriangleVerticesWithoutUVs = function ( pos, up, forwards, radius ) {

	// Create an equilateral triangle (only vertices)

	this.side.crossVectors( up, forwards ).multiplyScalar( radius * LightningStrike.COS30DEG );
	this.down.copy( up ).multiplyScalar( - radius * LightningStrike.SIN30DEG );

	var p = this.vPos;
	var v = this.vertices;

	p.copy( pos ).sub( this.side ).add( this.down );

	v[ this.currentCoordinate ++ ] = p.x;
	v[ this.currentCoordinate ++ ] = p.y;
	v[ this.currentCoordinate ++ ] = p.z;

	p.copy( pos ).add( this.side ).add( this.down );

	v[ this.currentCoordinate ++ ] = p.x;
	v[ this.currentCoordinate ++ ] = p.y;
	v[ this.currentCoordinate ++ ] = p.z;

	p.copy( up ).multiplyScalar( radius ).add( pos );

	v[ this.currentCoordinate ++ ] = p.x;
	v[ this.currentCoordinate ++ ] = p.y;
	v[ this.currentCoordinate ++ ] = p.z;

	this.currentVertex += 3;

};

LightningStrike.prototype.createTriangleVerticesWithUVs = function ( pos, up, forwards, radius, u ) {

	// Create an equilateral triangle (only vertices)

	this.side.crossVectors( up, forwards ).multiplyScalar( radius * LightningStrike.COS30DEG );
	this.down.copy( up ).multiplyScalar( - radius * LightningStrike.SIN30DEG );

	var p = this.vPos;
	var v = this.vertices;
	var uv = this.uvs;

	p.copy( pos ).sub( this.side ).add( this.down );

	v[ this.currentCoordinate ++ ] = p.x;
	v[ this.currentCoordinate ++ ] = p.y;
	v[ this.currentCoordinate ++ ] = p.z;

	uv[ this.currentUVCoordinate ++ ] = u;
	uv[ this.currentUVCoordinate ++ ] = 0;

	p.copy( pos ).add( this.side ).add( this.down );

	v[ this.currentCoordinate ++ ] = p.x;
	v[ this.currentCoordinate ++ ] = p.y;
	v[ this.currentCoordinate ++ ] = p.z;

	uv[ this.currentUVCoordinate ++ ] = u;
	uv[ this.currentUVCoordinate ++ ] = 0.5;

	p.copy( up ).multiplyScalar( radius ).add( pos );

	v[ this.currentCoordinate ++ ] = p.x;
	v[ this.currentCoordinate ++ ] = p.y;
	v[ this.currentCoordinate ++ ] = p.z;

	uv[ this.currentUVCoordinate ++ ] = u;
	uv[ this.currentUVCoordinate ++ ] = 1;

	this.currentVertex += 3;

};

LightningStrike.prototype.createPrismFaces = function ( vertex/*, index*/ ) {

	var indices = this.indices;
	var vertex = this.currentVertex - 6;

	indices[ this.currentIndex ++ ] = vertex + 1;
	indices[ this.currentIndex ++ ] = vertex + 2;
	indices[ this.currentIndex ++ ] = vertex + 5;
	indices[ this.currentIndex ++ ] = vertex + 1;
	indices[ this.currentIndex ++ ] = vertex + 5;
	indices[ this.currentIndex ++ ] = vertex + 4;
	indices[ this.currentIndex ++ ] = vertex + 0;
	indices[ this.currentIndex ++ ] = vertex + 1;
	indices[ this.currentIndex ++ ] = vertex + 4;
	indices[ this.currentIndex ++ ] = vertex + 0;
	indices[ this.currentIndex ++ ] = vertex + 4;
	indices[ this.currentIndex ++ ] = vertex + 3;
	indices[ this.currentIndex ++ ] = vertex + 2;
	indices[ this.currentIndex ++ ] = vertex + 0;
	indices[ this.currentIndex ++ ] = vertex + 3;
	indices[ this.currentIndex ++ ] = vertex + 2;
	indices[ this.currentIndex ++ ] = vertex + 3;
	indices[ this.currentIndex ++ ] = vertex + 5;

};

LightningStrike.prototype.createDefaultSubrayCreationCallbacks = function () {

	var random1 = this.randomGenerator.random;

	this.onDecideSubrayCreation = function ( segment, lightningStrike ) {

		// Decide subrays creation at parent (sub)ray segment

		var subray = lightningStrike.currentSubray;

		var period = lightningStrike.rayParameters.subrayPeriod;
		var dutyCycle = lightningStrike.rayParameters.subrayDutyCycle;

		var phase0 = ( lightningStrike.rayParameters.isEternal && subray.recursion == 0 ) ? - random1() * period : _Math.lerp( subray.birthTime, subray.endPropagationTime, segment.fraction0 ) - random1() * period;

		var phase = lightningStrike.time - phase0;
		var currentCycle = Math.floor( phase / period );

		var childSubraySeed = random1() * ( currentCycle + 1 );

		var isActive = phase % period <= dutyCycle * period;

		var probability = 0;

		if ( isActive ) {

			probability = lightningStrike.subrayProbability;
			// Distribution test: probability *= segment.fraction0 > 0.5 && segment.fraction0 < 0.9 ? 1 / 0.4 : 0;

		}

		if ( subray.recursion < lightningStrike.maxSubrayRecursion && lightningStrike.numSubrays < lightningStrike.maxSubrays && random1() < probability ) {

			var childSubray = lightningStrike.addNewSubray();

			var parentSeed = lightningStrike.randomGenerator.getSeed();
			childSubray.seed = childSubraySeed;
			lightningStrike.randomGenerator.setSeed( childSubraySeed );

			childSubray.recursion = subray.recursion + 1;
			childSubray.maxIterations = Math.max( 1, subray.maxIterations - 1 );

			childSubray.linPos0.set( random1(), random1(), random1() ).multiplyScalar( 1000 );
			childSubray.linPos1.set( random1(), random1(), random1() ).multiplyScalar( 1000 );
			childSubray.up0.copy( subray.up0 );
			childSubray.up1.copy( subray.up1 );
			childSubray.radius0 = segment.radius0 * lightningStrike.rayParameters.radius0Factor;
			childSubray.radius1 = Math.min( lightningStrike.rayParameters.minRadius, segment.radius1 * lightningStrike.rayParameters.radius1Factor );

			childSubray.birthTime = phase0 + ( currentCycle ) * period;
			childSubray.deathTime = childSubray.birthTime + period * dutyCycle;

			if ( ! lightningStrike.rayParameters.isEternal && subray.recursion == 0 ) {

				childSubray.birthTime = Math.max( childSubray.birthTime, subray.birthTime );
				childSubray.deathTime = Math.min( childSubray.deathTime, subray.deathTime );

			}

			childSubray.timeScale = subray.timeScale * 2;
			childSubray.roughness = subray.roughness;
			childSubray.straightness = subray.straightness;
			childSubray.propagationTimeFactor = subray.propagationTimeFactor;
			childSubray.vanishingTimeFactor = subray.vanishingTimeFactor;

			lightningStrike.onSubrayCreation( segment, subray, childSubray, lightningStrike );

			lightningStrike.randomGenerator.setSeed( parentSeed );

		}

	};

	var vec1Pos = new Vector3();
	var vec2Forward = new Vector3();
	var vec3Side = new Vector3();
	var vec4Up = new Vector3();

	this.onSubrayCreation = function ( segment, parentSubray, childSubray, lightningStrike ) {

		// Decide childSubray origin and destination positions (pos0 and pos1) and possibly other properties of childSubray

		// Just use the default cone position generator
		lightningStrike.subrayCylinderPosition( segment, parentSubray, childSubray, 0.5, 0.6, 0.2 );

	};

	this.subrayConePosition = function ( segment, parentSubray, childSubray, heightFactor, sideWidthFactor, minSideWidthFactor ) {

		// Sets childSubray pos0 and pos1 in a cone

		childSubray.pos0.copy( segment.pos0 );

		vec1Pos.subVectors( parentSubray.pos1, parentSubray.pos0 );
		vec2Forward.copy( vec1Pos ).normalize();
		vec1Pos.multiplyScalar( segment.fraction0 + ( 1 - segment.fraction0 ) * ( random1() * heightFactor ) );
		var length = vec1Pos.length();
		vec3Side.crossVectors( parentSubray.up0, vec2Forward );
		var angle = 2 * Math.PI * random1();
		vec3Side.multiplyScalar( Math.cos( angle ) );
		vec4Up.copy( parentSubray.up0 ).multiplyScalar( Math.sin( angle ) );

		childSubray.pos1.copy( vec3Side ).add( vec4Up ).multiplyScalar( length * sideWidthFactor * ( minSideWidthFactor + random1() * ( 1 - minSideWidthFactor ) ) ).add( vec1Pos ).add( parentSubray.pos0 );

	};

	this.subrayCylinderPosition = function ( segment, parentSubray, childSubray, heightFactor, sideWidthFactor, minSideWidthFactor ) {

		// Sets childSubray pos0 and pos1 in a cylinder

		childSubray.pos0.copy( segment.pos0 );

		vec1Pos.subVectors( parentSubray.pos1, parentSubray.pos0 );
		vec2Forward.copy( vec1Pos ).normalize();
		vec1Pos.multiplyScalar( segment.fraction0 + ( 1 - segment.fraction0 ) * ( ( 2 * random1() - 1 ) * heightFactor ) );
		var length = vec1Pos.length();
		vec3Side.crossVectors( parentSubray.up0, vec2Forward );
		var angle = 2 * Math.PI * random1();
		vec3Side.multiplyScalar( Math.cos( angle ) );
		vec4Up.copy( parentSubray.up0 ).multiplyScalar( Math.sin( angle ) );

		childSubray.pos1.copy( vec3Side ).add( vec4Up ).multiplyScalar( length * sideWidthFactor * ( minSideWidthFactor + random1() * ( 1 - minSideWidthFactor ) ) ).add( vec1Pos ).add( parentSubray.pos0 );

	};

};

LightningStrike.prototype.createSubray = function () {

	return {

		seed: 0,
		maxIterations: 0,
		recursion: 0,
		pos0: new Vector3(),
		pos1: new Vector3(),
		linPos0: new Vector3(),
		linPos1: new Vector3(),
		up0: new Vector3(),
		up1: new Vector3(),
		radius0: 0,
		radius1: 0,
		birthTime: 0,
		deathTime: 0,
		timeScale: 0,
		roughness: 0,
		straightness: 0,
		propagationTimeFactor: 0,
		vanishingTimeFactor: 0,
		endPropagationTime: 0,
		beginVanishingTime: 0

	};

};

LightningStrike.prototype.createSegment = function () {

	return {
		iteration: 0,
		pos0: new Vector3(),
		pos1: new Vector3(),
		linPos0: new Vector3(),
		linPos1: new Vector3(),
		up0: new Vector3(),
		up1: new Vector3(),
		radius0: 0,
		radius1: 0,
		fraction0: 0,
		fraction1: 0,
		positionVariationFactor: 0
	};

};

LightningStrike.prototype.getNewSegment = function () {

	return this.raySegments[ this.currentSegmentIndex ++ ];

};

LightningStrike.prototype.copy = function ( source ) {

	BufferGeometry.prototype.copy.call( this, source );

	this.init( LightningStrike.copyParameters( {}, source.rayParameters ) );

	return this;

};

LightningStrike.prototype.clone = function () {

	return new this.constructor( LightningStrike.copyParameters( {}, this.rayParameters ) );

};

export { LightningStrike };
