今回，
var lastMouse:Point;
var angularVelocity:Number = 5 * Math.PI / 180; // 一定値
function xDrag(eventObject:Event):void {
var currentMouse:Point = new Point(parent.mouseX, parent.mouseY);
var myMatrix:Matrix = transform.matrix;
myMatrix.translate(-lastMouse.x, -lastMouse.y);
myMatrix.rotate(angularVelocity); // 回転
myMatrix.translate(currentMouse.x, currentMouse.y);
transform.matrix = myMatrix;
lastMouse = currentMouse.clone();
}
後編の今回は，
ドラッグする位置と向きと速さによって回転を加速する
前編で，
図1 インスタンスを回す速さはふたつのベクトルで決まる
インスタンスのドラッグで回転を加速するアニメーションのリスナー関数
var lastMouse:Point;
var angularVelocity:Number = 0;
var deceleration:Number = 0.8;
var ratio:Number = 5 / width / height;
function xDrag(eventObject:Event):void {
var currentMouse:Point = new Point(parent.mouseX, parent.mouseY);
var myMatrix:Matrix = transform.matrix;
var position:Point = new Point(x, y);
// 外積を求めるふたつのベクトルの計算
var radius:Point = lastMouse.subtract(position);
var force:Point = currentMouse.subtract(lastMouse);
var moment:Number = crossProduct2D(radius, force);
angularVelocity += moment * ratio;
myMatrix.translate(-lastMouse.x, -lastMouse.y);
myMatrix.rotate(angularVelocity);
myMatrix.translate(currentMouse.x, currentMouse.y);
transform.matrix = myMatrix;
lastMouse = currentMouse.clone();
angularVelocity *= deceleration;
}
function crossProduct2D(point0:Point, point1:Point):Number {
var vector0:Vector3D = new Vector3D(point0.x, point0.y, 0);
var vector1:Vector3D = new Vector3D(point1.x, point1.y, 0);
var crossProduct3D:Vector3D = vector0.crossProduct(vector1);
return crossProduct3D.z;
}
ベクトルはPointオブジェクトで定めた。インスタンスの基準点は中心に定めたので，
引かれるPointオブジェクト.subtract(引くPointオブジェクト)
新たに加えた関数
ただし，
これで，
スクリプト1 インスタンスをドラッグで加速して回す
// フレームアクション: マウスでドラッグして回すMovieClipシンボル
var lastMouse:Point;
var angularVelocity:Number = 0;
var deceleration:Number = 0.8;
var ratio:Number = 5 / width / height;
addEventListener(MouseEvent.MOUSE_DOWN, xMouseDown);
function xMouseDown(eventObject:MouseEvent):void {
lastMouse = new Point(parent.mouseX, parent.mouseY);
addEventListener(Event.ENTER_FRAME, xDrag);
stage.addEventListener(MouseEvent.MOUSE_UP, xMouseUp);
}
function xMouseUp(eventObject:MouseEvent):void {
removeEventListener(Event.ENTER_FRAME, xDrag);
stage.removeEventListener(MouseEvent.MOUSE_UP, xMouseUp);
}
function xDrag(eventObject:Event):void {
var currentMouse:Point = new Point(parent.mouseX, parent.mouseY);
var myMatrix:Matrix = transform.matrix;
var position:Point = new Point(x, y);
var radius:Point = lastMouse.subtract(position);
var force:Point = currentMouse.subtract(lastMouse);
var moment:Number = crossProduct2D(radius, force);
angularVelocity += moment * ratio;
myMatrix.translate(-lastMouse.x, -lastMouse.y);
myMatrix.rotate(angularVelocity);
myMatrix.translate(currentMouse.x, currentMouse.y);
transform.matrix = myMatrix;
lastMouse = currentMouse.clone();
angularVelocity *= deceleration;
}
function crossProduct2D(point0:Point, point1:Point):Number {
var vector0:Vector3D = new Vector3D(point0.x, point0.y, 0);
var vector1:Vector3D = new Vector3D(point1.x, point1.y, 0);
var crossProduct3D:Vector3D = vector0.crossProduct(vector1);
return crossProduct3D.z;
}
図2 マウスのドラッグでインスタンスの回る速さが加速する
