パーティクルやってみた2
物体がお互いに引っ張り合います。
万有引力の公式
引力 = G * 物体1の質量 * 物体2の質量 / (物体間の距離)^2
Gは定数で気にしなくてもよいそうなので。
引力 = 物体1の質量 * 物体2の質量 / (物体間の距離)^2
この式を利用しています。
ソース
package { import __AS3__.vec.Vector; import flash.display.Sprite; import flash.display.StageAlign; import flash.display.StageScaleMode; import flash.events.TimerEvent; import flash.filters.BlurFilter; import flash.geom.Point; import flash.utils.Timer; [SWF(width="512", height="512", backgroundColor="0x000000")] public class Animation_Particle extends Sprite { private var particles:Vector.<Ball>; private var numParticles:uint = 100; private var timer:Timer; public function Animation_Particle() { stage.scaleMode = StageScaleMode.NO_SCALE; stage.align = StageAlign.TOP_LEFT; init(); } //初期化 private function init():void{ particles = new Vector.<Ball>(); for(var i:uint = 0; i < numParticles; i++){ var size:Number = Math.random() * 20 + 5; var particle:Ball = new Ball(5); particle.filters = [new BlurFilter(2, 2, 5)]; particle.x = Math.random() * stage.stageWidth; particle.y = Math.random() * stage.stageHeight; particle.mass = size; addChild(particle); particles.push(particle); } timer = new Timer(33); timer.addEventListener(TimerEvent.TIMER, loop); timer.start(); } private function loop(event:TimerEvent):void{ for(var i:uint = 0; i < numParticles; i++){ var particle:Ball = particles[i]; particle.x += particle.vx; particle.y += particle.vy; } for(i = 0; i < numParticles - 1; i++){ var partA:Ball = particles[i]; for(var j:uint = i + 1; j < numParticles; j++){ var partB:Ball = particles[j]; checkCollision(partA, partB); gravitate(partA, partB); } } } //引力の計算 private function gravitate(partA:Ball, partB:Ball):void{ var dx:Number = partB.x - partA.x; var dy:Number = partB.y - partA.y; var distSQ:Number = dx * dx + dy * dy; var dist:Number = Math.sqrt(distSQ); var force:Number = partA.mass * partB.mass / distSQ; var ax:Number = force * dx / dist; var ay:Number = force * dy / dist; partA.vx += ax / partA.mass; partA.vy += ay / partA.mass; partB.vx -= ax / partB.mass; partB.vy -= ay / partB.mass; } private function checkCollision(ball0:Ball, ball1:Ball):void { var dx:Number = ball1.x - ball0.x; var dy:Number = ball1.y - ball0.y; var dist:Number = Math.sqrt(dx*dx + dy*dy); if(dist < ball0.radius + ball1.radius) { // 角度とサイン、コサインの計算 var angle:Number = Math.atan2(dy, dx); var sin:Number = Math.sin(angle); var cos:Number = Math.cos(angle); // ball0の位置の回転 var pos0:Point = new Point(0, 0); // ball1の位置の回転 var pos1:Point = rotate(dx, dy, sin, cos, true); // ball0の速度の回転 var vel0:Point = rotate(ball0.vx, ball0.vy, sin, cos, true); // ball1の速度の回転 var vel1:Point = rotate(ball1.vx, ball1.vy, sin, cos, true); // 衝突反応 var vxTotal:Number = vel0.x - vel1.x; vel0.x = ((ball0.mass - ball1.mass) * vel0.x + 2 * ball1.mass * vel1.x) / (ball0.mass + ball1.mass); vel1.x = vxTotal + vel0.x; // 位置の更新 var absV:Number = Math.abs(vel0.x) + Math.abs(vel1.x); var overlap:Number = (ball0.radius + ball1.radius) - Math.abs(pos0.x - pos1.x); pos0.x += vel0.x / absV * overlap; pos1.x += vel1.x / absV * overlap; // 位置の回転 var pos0F:Object = rotate(pos0.x, pos0.y, sin, cos, false); var pos1F:Object = rotate(pos1.x, pos1.y, sin, cos, false); // 実際の画面位置への調整 ball1.x = ball0.x + pos1F.x; ball1.y = ball0.y + pos1F.y; ball0.x = ball0.x + pos0F.x; ball0.y = ball0.y + pos0F.y; // 速度の回転 var vel0F:Object = rotate(vel0.x, vel0.y, sin, cos, false); var vel1F:Object = rotate(vel1.x, vel1.y, sin, cos, false); ball0.vx = vel0F.x; ball0.vy = vel0F.y; ball1.vx = vel1F.x; ball1.vy = vel1F.y; } } private function rotate(x:Number, y:Number, sin:Number, cos:Number, reverse:Boolean):Point { var result:Point = new Point(); if(reverse) { result.x = x * cos + y * sin; result.y = y * cos - x * sin; } else { result.x = x * cos - y * sin; result.y = y * cos + x * sin; } return result; } } }