Move object to target smoothly

simonwilson • 2022-08-17 2022-08-17 19:02 •

BBS>

PICO-8>Tutorials

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

by simonwilson

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

movement speed friction slow transition math formula mode

JadeLombax • 2022-08-17*2022-08-17 19:39*

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.

SealProgrammer • 2022-08-17*2022-08-17 23:06*

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 SealProgrammer

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

profpatonildo • 2022-08-18 2022-08-18 00:16

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.