HELP NEEDED: Player resisting to momentum

[rigid lotus]

Hi, i need help with something slightly complicated. I've got my player, who moves with acceleration (very short acceleration). The player can press a certain key, and send out a vine. if the vine catches a pole, it will pull the player towards it with momentum. Everything is fine, except when i want to cancel the momentum, and i press left key to face the other direction, the player negates it (as intended), but than, the second i leave the key, his speed goes back to the momentum speed, (which looks weird). I already know the source of the problem, and it is in the line where i set the player horizontal speed (hsp):

hsp = ((key_right - key_left) * SPD_WALK) + round(vineMomentum);

This is because we are SETTING the hsp, and we aren't lowering the vineMomentum. I wonder if there is a way to fix this, i know i probably have to redo how the hsp works, im guessing i have to do += but stuck on how to make it work. Help would be much appreciated!!!

[keen mesa]

Could try something like this maybe?

var horizontalInput  = key_right - key_left;

if (horizontalInput != 0 && sign(horizontalInput) != sign(vineMomentum)) vineMomentum = 0;

Though it would probably look better if you rapidly reduced vine momentum rather than just instantly setting it to 0.

Maybe something like:

var horizontalInput  = key_right - key_left;

if (horizontalInput != 0 && sign(horizontalInput) != sign(vineMomentum)) vineMomentum = vineMomentum *.1;
if (vineMomentum !=0 && abs(vineMomentum) < someNumber) vineMomentum =  0;

[rigid lotus]

Hey, thanks for answering! what would i be setting the hsp to, after this?

[keen mesa]

hsp = ((key_right - key_left) * SPD_WALK) + round(vineMomentum);

Still this, right? You could just zero out vineMomentum so that it's no longer affecting the hsp calculation.

Assuming I'm understanding where the issue is coming from.

Right now you are adding two numbers, SPD_WALK which is affected by inputs, and vineMomentum which is not. So when you hold left, SPD_WALK is negative so it is acting against vineMomentum, which in your example video is positive. But it's not reducing the numerical value of vineMomentum.

So when you let go of the button it's no longer acting against vineMomentum, so you start accelerating to the right.

This looks to see if your input direction is moving you in the opposite direction of vineMomentum and if you are it sets it to 0, so that when you let go of the direction key you should just drop, since vineMomentum has been set to zero.

var horizontalInput  = key_right - key_left;

if (horizontalInput != 0 && sign(horizontalInput) != sign(vineMomentum)) vineMomentum = 0;

At least that's how it's working in my head?

[rigid lotus]

ohhhhhhhhhhh, i undertand the issue now, thanks for explaining it so well. i think ill want to reduce it gradually, since i dont want it to be that easy to resist to the momentum

[rigid lotus]

but what i didnt understand is why this line:
if (vineMomentum !=0 && abs(vineMomentum) < someNumber) vineMomentum = 0;

[keen mesa]

So, vine momentum is gonna be negative if you are vining to the left and positive if you are vining to the right, yeah?

So an easy way to have it approach zero rather than snap to it is to multiply it by a fraction. But you want it to reach zero eventually. And if you're always, for example, multiplying by .10 it will never actually reach zero. It'll just keep getting smaller and smaller.

So you look at the absolute value of vine momentum, check to see if it is smaller than some very small number, and, if so, set it to 0.

[rigid lotus]

so Somenumber shoud be like 1 or something right?

or 0.1 etc

[keen mesa]

IDK what code you have that may be affecting vine momentum in the background. That was just a quick way of making sure it gets to 0 eventually.

Yeah.

[rigid lotus]

ok, thats great, but for example i want the resistance to be weaker, i up the * .1 to * .99 right?

[keen mesa]

Absolutely.

Just play with the numbers until you get the feel you want. Movement rarely works well on the first go.

(for me lol)

[rigid lotus]

so that's what i did, and than i saw that the bug is still happening

[rigid lotus]

its kinda hard to see but do you notice how the player speed goes back up again the second i stop resisting?

[keen mesa]

What if you do .1? Still getting the unexpected movement?

[rigid lotus]

no, but thats because the resistance is way too large

[keen mesa]

Well 1% per frame is pretty close to nothing.

So you'll need to play with the numbers until you get the effect you want.

[rigid lotus]

Yes, but is there a way to completely eliminate the bug where the player speed goes back up, whatever the resistence is? it just feels really janky

because it feels weird that i press, than leave, and suddenly my speed goes back up

[keen mesa]

That is going to happen as long as vineMomentum is greater than zero and this calculation is happening:

hsp = ((key_right - key_left) * SPD_WALK) + round(vineMomentum);

You will either need to zero out vine momentum or you will need to implement a state change where different movement rules are applied during the 'vine zip' state.

I haven't done a lot of platforming stuff, so I don't know that I could give you a formula that's going to be smooth right off the bat. If you want to send me a YYZ, I'd be happy to play with the numbers.

[rigid lotus]

Sure, by yyz you mean package right?

[keen mesa]

Yep. Zip file of the package.

[rigid lotus]

ok, but the file is too large to send on discord, i tried earlier removing unnecessary stuff from the package but because of my crappy code a lot of the objects rely one on another (definitely going to remove a lot of objects and code once im done with the movement)

187,839 kb

[keen mesa]

That's pretty big. If you want to toss it on a hosting service or whatever, I'll download it.

Google drive, github, whatever works.

[rigid lotus]

like ive got a repo on github i can share with you...?
thank you so much btw

[keen mesa]

That works.

No problem. Again, platformers aren't really what I've mostly worked on... so no promises. But hopefully I can find a working solution.

[rigid lotus]

okay! heres the url
https://github.com/Rafimock/An-Apple.git
the branch we are currently working on is vinepull-Rework #1 (the one with the small v)

[rigid lotus]

do i have to make my repo public or add you as a colaborator?

[keen mesa]

Yeah, one or the other.

I'll just download a copy and work on that once I can get to it.

[rigid lotus]

Ok, thank you so much! What is your name on GitHub? (If I don't mind me adding you as a collaborator)

[keen mesa]

yeahchris

[rigid lotus]

ok i sent you an invite

[keen mesa]

Well, this feels better. Give it a try:

    var horizontalInput  = key_right - key_left;

    if (sign(horizontalInput) == -sign(vineMomentum)) vineMomentum = vineMomentum *.98;
    if (vineMomentum !=0 && abs(vineMomentum) < 1) vineMomentum =  0;
    if (vineMomentum == 0)hsp = ((key_right - key_left) * SPD_WALK); // * vineMomentum
    else hsp = vineMomentum;

Not 100% sure it's what you want.

It feels a lot better if you wait for vineMomentum to be fully negated before allowing inputs to add/subtract SPD_WALK from hsp.

Though this change also stops them from adding to their speed if they press move towards the vine pull. But that can be rectified if you want that to happen.

[rigid lotus]

Hey, sorry for not responding for a while, thank you so much for putting the time in and helping! im trying it out now

[rigid lotus]

Yes! It works Perfectly! but it also causes another issue - the Momentum is wayyyy to much when i dont press any key, im maybe going to try and nerf the momentum and see if that fixes it...

[keen mesa]

Yeah, that should just be a matter of tweaking the initial value of vine momentum wherever that gets initially set.

[rigid lotus]

There's still an issue though, even if i nerf the vine momentum, if you hold the direction of the momentum, the second you touch the floor, you can notice that you can't move because vinemomentum is still decreasing, which kinda interupts the flow....

sorry for being so nitpicky

[keen mesa]

Lemme check what you mean.

I'm not seeing that? This is if you're holding the movement key in the direction that you are vine whipping?

[rigid lotus]

yes, maybe because of the platforms, move some of them out of the way, than vinepull and keep holding that key, you will see that when you land on the floor and expect to keep moving, you are slower because vineMomentum isn't 0 yet.

[keen mesa]

Oh, okay. I think I get what you mean. You just want to allow movement slightly earlier if you are landing on the ground?

But without allowing for a mid-air trajectory that looks like this:

[rigid lotus]

yes, exactly

but it also works if i change the snapping to 3

something like that

[keen mesa]

How are you doing collision? Not finding the code right away.

[rigid lotus]

move_and_collide

[keen mesa]

Tiles or objects?

[rigid lotus]

objects, with oWall

[keen mesa]

Cool.

I was thinking just put a check to see if there's a floor a few pixels away using an OR statement.

[rigid lotus]

it's in a function called FallAndCollide(), there i handle gravity, jumping and collisions, since i want those to be called by multiple states

[keen mesa]

Makes sense.

[rigid lotus]

thats fixed though so its fine, but theres another bug now😭

[keen mesa]

Naturally.

[rigid lotus]

fsr now, every time i vinepull the distance is larger than the previous one

[keen mesa]

Distance meaning vineMomentum or something else?

[rigid lotus]

yup

[keen mesa]

Well, you have a vineMomentumMax variable. If its getting larger than you want that means somewhere in the code where you are setting the initial value of vineMomentum you are probably not clamping it to max out at vineMomentumMax.

Where do you set up vineMomentum?

Found it.

[rigid lotus]

nevermind, the bug was caused by me

sorry

fsr i just deleted a line of code that reset freeHsp and vineAddedMomentum

[keen mesa]

Oh, okay. So all good now?

[rigid lotus]

It's really hard to recreate but if i resist at a certain time, i just cant move (also when i land)

[keen mesa]

Like, at all? You get stuck?

Trying to recreate it, but not having much luck.

You could try just zeroing out vineMomentum with that same check to see if you're about to land.
(though this may create an issue if you intend to let your player zip at high speed just over land using the vine whip. It might be better to do it in your collision code, just before the move_and_collide.)

I can't recreate the error with the copy I have downloaded. Not sure if the bug doesn't exist in my copy or whether the timing is just hyper-precise.

[rigid lotus]

its ok, i think the bug is rooted in another issue

[rigid lotus]

untill now everything seems pretty solid, im going to spend a while just trying to make sure it works, thank you so much!!!!!!