ドラクエ式縦列パーティ

いいかんじの距離で後ろについてくる縦列パーティ↑のロジック
ストリートファイターのコマンド入力もこんな感じのロジックだと聞いた。

var party	= new Party(
    new Member(0),new Member(1),new Member(2),
    new Member(3),new Member(5),new Member(6),
    new Member(7),new Member(8),new Member(9),
    new Member(10)
)
var camera	= new Camera(...party.items)
party.camera = camera.delta

class Party{
	constructor(...a){
		this.items		= a
		this.track		= [new Vector(0,0)]
		this.position	= new Vector(0,0)
		this.camera		= null
		this.gap 		= 60
	}
	update(vector){//コントローラーのスティック入力など渡し
		var compass		= vector.rotate(this.camera.yaw)//進行方向
		var delta		= compass.mul(4)
		this.position	= this.position.add(delta)	
		this.position.push(delta.magnitude)//長さキャッシュ
		this.track.unshift(this.position)

        //メモ添付
		var track		= this.track
		for(var i=0;i<this.items.length;i++){
			var member		= this.items[i]
			var position	= track[0]
			var vector		= position.sub(track[1])
			member.position	= position.sub(this.position)
			member.vector	= vector
			member.direction(vector.rotate(-this.camera.yaw))
			
			var distance	= 0
			var j = track.findIndex(p=>(distance+=p[2])>this.gap)
			if(j==-1||j==track.length-1) break
			
			var front = track[j-1]
			var back  = track[j]
			var delta = distance - this.gap
			var vector = front.sub(back).mul(delta/front[2])
			var position = back.add(vector)
			position.push(vector.magnitude)
			track = track.slice(j)
			track.unshift(position)
		}
		return this.shoot()
	}
	shoot(){//パン・チルト
		this.items.forEach(v=>{
			v.rotate(-this.camera.pitch,-this.camera.yaw)
			v.direction(v.vector.rotate(-this.camera.yaw))
		})
		return this
	}
}

パーティ追尾仕様

勇者の足跡をストックしておき、ピッタリの間隔になるようにベクトル補完。
しっかり処理すると追尾のカクツキが消えます。

---

簡易Vector2
javascriptでもスカラー風に四則演算書けたらいいのにね

class Vector extends Array{//Vector2
	get x()			{return this[0]}
	get y()			{return this[1]}
	get magnitude()	{return Math.hypot(this[0],this[1])}
	get radian()	{return this.length?Math.atan2(this[1],this[0]):0}
	get degree()	{return this.radian*Vector.R2D}
	get square()	{return this[0]*this[0]+this[1]*this[1]}//sqrMagnitude
	set degree(d){
		var r = d/Vector.R2D
		var m = this.length?this.magnitude:1
		this[0] = Math.cos(r)*m
		this[1] = Math.sin(r)*m
	}
	add(a){return new Vector(this[0]+a[0],	this[1]+a[1]	)}
	sub(a){return new Vector(this[0]-a[0],	this[1]-a[1]	)}
	mul(n){return new Vector(this[0]*n,		this[1]*n		)}
	div(n){return new Vector(this[0]/n,		this[1]/n		)}
	rotate(d){//rotateZ
		var v = this.slice()
		v.degree += d
		return v
	}
}
Vector.R2D = 180/Math.PI