How to get a pleasant path accelerating to a point

Question

I am having trouble moving an object to a target position with a maximum acceleration limit.

If i just accelerate towards the target the object will fly in a doughnut a few times before hitting the target. example

If i first accelerate to reduce the vector rejection i get a nasty path directly away from the target and then a line straight to the target. example

Any ideas how to move in a natural human-like path?

edit

I now move in a circle at current speed with maximum acceleration until i am facing the target then accel towards it example1 example2

its not perfect but its quite predictable for players and i can calcuate time to reach target in constant time now (yey)

if anyone wants a break down of the math i can explain

possible duplicate of How do I make a vehicle move to a point and stop without overshooting or oscillating? — Seth Battin, Jul 12 '15 at 22:50
@SethBattin i dont care about stopping at the point, just moving to it, final velocity is irrelevant for this problem — t123, Jul 12 '15 at 22:51
Can you clarify what you meant by "doughhnut", then? That made me imagine that you were trying to stop at a point and wrongly orbiting it briefly. Or as that duplicate described it, oscillating. — Seth Battin, Jul 12 '15 at 22:53
Needs clarification for "natural" and "human-like". Nobody agrees on their meanings. — Anko, Jul 12 '15 at 23:17
@tm1rbrt it looks you have constraints on your motion that you didn't mention. Why does acceleration happen in any direction other than toward the target? And your second image makes almost no sense; why doesn't the path lead toward the target immediately? — Seth Battin, Jul 13 '15 at 14:35
@SethBattin i was adding (the normalizing total) acceleration to reduce my vector rejection (current_velocity, direction_to_target) to try and reduce the doughnutting (see example two). It works really great except for when the target is too close to the origin — t123, Jul 13 '15 at 20:35

driima · Answer 1 · 2015-07-13T02:45:09.117

You could try setting a threshold from the target, and multiplying the object's speed by distance / threshold:

acceleration = distance / threshold

if (acceleration <= 1) {
    speed *= acceleration;
}

Here's an interactive example I threw together quickly:

https://dl.dropboxusercontent.com/u/38185080/Flash/Examples/Deceleration.swf

Checking gradual movement will set speed to the acceleration value regardless of whether or not it is a value less than one. Without it checked, the speed will always equal the max speed unless it is within the threshold - it uses the same code displayed above, slightly modified:

if (gradual) {
    speed = acceleration;
} else {
    speed = maxSpeed;

    if (acceleration <= 1) {
        speed *= acceleration;
    }
}

Now you all you do is add the object direction to its position and multiply it by speed:

position += direction * speed;

Alan Wolfe · Answer 2 · 2015-07-13T02:17:58.050

0

If you don't need a strictly physics based solution, bias and gain can be great for giving a nice organic (accel / decel) feel to a simple linear interpolation.

http://blog.demofox.org/2012/09/24/bias-and-gain-are-your-friend/ http://demofox.org/biasgain.html

edited Jul 13 '15 at 02:17

answered Jul 13 '15 at 01:02

Alan Wolfe

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How to get a pleasant path accelerating to a point

2 Answers2