I need some help with the math for making an object move between 2 fixed positions, then slow down smoothly to the final position.

The cart contains my attempt to make this work but I cannot quite reach the end point, and therefore the mode variable does not change.

Can anyone see what is missing here, and what could I do to make the last few steps a bit faster? (It slows to a crawl at the end...!)

Many thanks in advance :)

demenifji

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demenifji

by simonwilson

Cart #demenifji-0 | 2022-08-17 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA

1

The problem seems to be that once the remaining distance is small enough, its value/100 is, as far as Pico-8 is concerned, equal to zero. Probably the simplest fix would be just to add a small constant value to the velocity.

Try this!

function _init()
 mode="move"

    start=10
    finish=110

    pl_x=start
    pl_y=64
    pl_sp=1
    pl_dx=4

end

function _update()
    if mode=="move" then
    -- using mode to stop drifting
        distance=finish-pl_x
        pl_x+=(pl_dx*(distance/100)+0.2)
        --above line changed
    end
    if pl_x >= finish then
        pl_dx=0
        mode="wait"
    end
end

function _draw()
 cls()
    circ(pl_x,pl_y,3,8)
    pset(start,64,10)
    pset(finish,64,10)
    print(distance)
    print("mode: "..mode)
end

Idea

by MrAwesome

Cart #zapiwojoba-0 | 2022-08-17 | Code ▽ | Embed ▽ | No License

1

Simply change:

if pl_x >= finish then
    pl_dx=0
    mode="wait"
end

for

if abs(distance) < 0.1 then
    pl_dx=0
    pl_x=finish
    mode="wait"
end

0.1 there is an arbitrary value, it could be 1, 0.5, whatever you want to be the threshold to "snap" into the finish position. Doing that should work.

you need an easing function!
https://www.lexaloffle.com/bbs/?tid=40577

@JadeLombax @MrAwesome @profpatonildo @merwok

Thanks all for your responses! All your suggestions had a nice effect and to follow on I am now trying out some more easing functions. :)