javascript中的弧

Question

您好我一直在关注炮弹物理以及如何在游戏中实施它们。

我想将重力应用于炮弹以及相对于鼠标的x和y速度 光标位置。所以炮弹向你的鼠标位置移动。

远离鼠标光标（从大炮开始），速度越高。

角度应与画布上光标的位置匹配。

我现在已经花了好几天的时间，所以现在我问。

谁知道使用javascript和canvas的好的炮弹物理？

    units = 10,
pixelsPerMeter = stage.width / units,
startlaunch = Math.PI/4,
launchAngle = startlaunch;

bang = {
    lastTime: 0,
    gravity: 9.81,

    applyGravity: function (elapsed) {
        bullet1.velocityY = (this.gravity * elapsed) -
                            (launchVelocity * Math.sin(launchAngle));
    },

    updateBulletPosition: function (updateDelta) {

        bullet1.left += bullet1.velocityX * (updateDelta) * pixelsPerMeter;
        bullet1.top += bullet1.velocityY * (updateDelta) * pixelsPerMeter;
    },

    execute: function (bullet1, time) {
        var updateDelta,
            elapsedFlightTime;
            if(bulletInFlight){
                elapsedFrameTime = (time - this.lastTime)/1000;
                elapsedFlightTime = (time - launchTime)/1000;

                this.applyGravity(elapsedFlightTime);
                this.updateBulletPosition(elapsedFrameTime);
            }
            this.lastTime = time;
    }
}


cannon.rotation = cannon.on("tick", function(event) {
    var angle = Math.atan2(stage.mouseY - cannon.y, stage.mouseX - cannon.x );
    angle = angle * (180/Math.PI);
     // The following if statement is optional and converts our angle from being
    // -180 to +180 degrees to 0-360 degrees.  It is completely optional
    if(angle < 0){
        angle = 360 - (-angle);}
    // Atan2 results have 0 degrees point down the positive X axis, while our image is pointed up.
    // Therefore we simply add 90 degrees to the rotation to orient our image
    // If 0 degrees is to the right on your image, you do not need to add 90
    cannon.rotation = 90 + angle;
     });

var fire = false, gravity = 6, vy = 3, vx = 3;

oneback.on("click", function(e) {

        bullet1.x = cannon.x;
        bullet1.y = cannon.y;
        scene1.addChild(bullet1);
        fire = true;

//e.preventDefault();

bullet1.rotation = cannon.rotation;

if(fire == false){
    bullet1.vx = Math.cos(bullet1.x-stage.mouseX) * this.vx;// used to be... this.bullet_speed'.
    bullet1.vy = Math.sin(bullet1.y-stage.mouseY) * this.vy;
}
});

oneback.on("click", function(e){

e.preventDefault();

if(fire == true) {
    loc = (stage.mouseX, stage.mouseY);
    lastMouse.left = loc.x;
    lastMouse.top = loc.y;

    deltaX = Math.abs(lastMouse.left - bullet1.left);
    deltaY = Math.abs(lastMouse.top - bullet1.top);

    launchAngle = Math.atan(parseFloat(deltaY) / parseFloat (deltaX));
    launchVelocity = 4 * deltaY / Math.sin (launchAngle) / pixelsPerMeter;
 }
 });



bullet1.on("tick", function(event){
    if(fire == true){
        bullet1.y += vy - gravity;
        bullet1.x += vx - gravity;

        // bullet1.y -= stage.mouseY;
        //bullet1.x -= stage.mouseX;
        //bullet1.x = direction - gravity;
        //bullet1.y = direction - gravity;
        }


});