我的动画的缓动功能不起作用

Question

I'm not the best at maths, and im sorta trying to guess how to implement this for my animation. But currently it is not working, and I believe i have misunderstood how to do my easing function for my animation.

I have a object which is meant to represent a plane, on my canvas of which has the follow properties:

Current Velocity    = obj.velocity
Braking Distance    = obj.stopDist
Current Position    = obj.posX & obj.posY
Destination         = obj.destX & obj.destY

So i then incorporate the maths to try to have the plane land on a runway with an easing function so it looks half decent visually even if its not real world physics like this:

function ease(easeDelta,accelerateBool){
    if(accelerateBool){
          // accelerating
          return (easeDelta * easeDelta * easeDelta);
    } else {
         //decelerating
          return ((easeDelta--) * easeDelta * easeDelta + 1);
        }

}
function InRange(delta, minValue, maxValue){
     var range        = (maxValue - minValue);
     var valueInRange = (range * delta); 
     var finalValue   = (valueInRange + minValue);
     return finalValue;
}

function landing(){ //part of animation loop
 var delta        = new Date().getTime() - obj.timer, //ms since previous frame         
     vectorX      = obj.destX - obj.posX,
     vectorY      = obj.destY - obj.posY,
     normal       = Math.sqrt(vectorX*vectorX + vectorY*vectorY), //distance to destination
     targetSpeed  = 20,
     easeDelta    = (normal / obj.stopDist),
     newSpeed     = InRange(ease(easeDelta,false), obj.velocity, targetSpeed),
     distance     = delta * newSpeed;

     obj.posX    += (distance * vectorX);
     obj.posY    += (distance * vectorY);
     obj.timer    = new Date().getTime(); //ready for next frame    
}

The problem is the plane doesn't slow down as it goes a long the runway towards its destination. It just stays really slow.

Have i confused my maths with how easing functions work ?

Answer 1

Here are some extremely simple easing in and out equations written in that you might find helpful.

  // accelerating from zero velocity
  function easeIn(t)
  {
    return t*t
  }

  // decelerating to zero velocity
  function easeOut(t) 
  { 
    return t*(2-t) 
  }

so you could use them like so:

function ease(easeDelta,accelerateBool){
    if(accelerateBool){
          // accelerating
          return (easeDelta * easeDelta);
    } else {
         //decelerating
          return ((easeDelta*(easeDelta - 2)));
        }

}