Creep curving, and how to fix it.

qwert-chan · Jul 29, 2012

How to: Fix Warcraft 3 creep pathfinding.

What is the problem, man?

A few months ago, when I decided to create my own Tower Defense, I had a lot of trouble with creeps: they just didn't want to walk in a straight line. You see, when you pick a unit and order him to move somewhere far away, he "curves", and goes a little bit to the side of his target, and then, when he's almost there - he changes directions and comes to the right place.
This can be extremely annoying in some cases.
Let me show you an illustration.

Here is a map called "Path test" which is pretty self-explanatory. It has a trigger:

Events
Player - Player 1(red) types a chat message containing next as Exact match
Actions
Unit - Create 1 Dryad for Player 1(red) at (Center of Location 000 <gen) facing 270.00 degrees.
Unit - Order(last created unit) to Move (Center of Location 001 <gen)

And when you type "next" to run the trigger, your dryad runs down and a bit to the right, almost running off the brick road.
Like that:
Top point:

Middle point:

Bottom point:

Her trajectory is like that:

And she runs on a purple line instead of a red one.
Now, most people recommend using path blockers, increasing the number of locations, but these ways are not always applicable, and creep movement still remains weird. And I know that is not really important ^^ but is visually implausible and can turn your Maze-like TD with a lot of narrow paths into a mess.

So, what should we do?

Simply change your unit's property "Movement - Type" to "Hover", and "Pathing - Collision Size" to 1.
And her trajectory now is correct:

Yes, it is simple as that =)

Thank you!

And by the way, you can check out a map in the attachment to see it for yourself.

iChaos · Jul 29, 2012

So simple, maybe? I recommend you to add another picture/screenshot featuring that the dryad walked real straight in the line, in that way, even if without testing it would be much more believable. Also I THINK this is somewhat short, mind in adding additional informations or other things?

Almia · Jul 29, 2012

Regions,you can use dummies with the event.
[trigger=] Unit - a unit comes within 500 range of Dummy <gen>[/trigger]
Just like that.

qwert-chan · Jul 29, 2012

Whoa, that was quick! Thank you for your feedback, everyone.
Silly me, I forgot to attach a test map. =)
And you'll need to change the creep's size as well to make it work.(that's what happens when you spend half of your day in the WE ^^")
iChaos
I've added a bit more info and screenshots - hope that helps.
Radamantus
Yes, I know that regions are not very efficient and there are better ways - but I chose them to exclude possible creep collision problems.

Almia · Jul 30, 2012

In DotA,they use that method i said before because Conditions doesnt read it.

iChaos · Jul 31, 2012

Nicer.

PurgeandFire · Jul 31, 2012

Nice job overall. This tutorial may be simple but not many people know that the solution is that easy--I certainly didn't. I've seen a lot of maps where this was a problem too.

Approved.

iChaos · Aug 5, 2012

Told ya, nao it is approved. :ogre_haosis:

qwert-chan · Aug 7, 2012

Thanks everyone for your help :3 glad it got approved.)

deathismyfriend · Oct 24, 2012

creep curving issue

hello im new to map making i cant find out how to fix the creep curving issue i tried to change movement-type to float and pathing-collision size to 1 but the unit doesnt move when spawn even on ur test map it just sits at the spawn point can anyone help plz and thanks to anyone tht does

PurgeandFire · Oct 24, 2012

You have to type "next" in the test map and enter it. (in chat) The units don't move unless this event is fired:

Player - Player 1(red) types a chat message containing next as Exact match

You can change that to whatever you'd like and whenever that event happens, the unit will move.

deathismyfriend · Oct 25, 2012

i know how to type it in i meant the creeps dont work the way they r supposed to
when i type next and when the pathing is change and movement type is change the units spawn and just sit in one spot

Frotty · Nov 1, 2012

He is correct.
Changing the movementtype to Float makes the unit unable to move.
Did anybody actually test this?

PurgeandFire · Nov 1, 2012

Hmm yeah it doesn't seem to work. Actually, the fields that he refers to "Path-Size" doesn't seem to exist (in the object editor, anyway). Maybe he is using a different language for his editor. If anyone knows which fields he is referring to, PM me. Otherwise, I'll send this to the graveyard for now since it doesn't seem to work.

Sorry about the confusion.

PurgeandFire · Jul 1, 2013

The tutorial has been updated thanks to qwert-chan. Approved.

Frotty · Jul 22, 2016

No, I still don't get why this is approved.
Even in the test map, when I set the dryad to hover and collision 1, it still curves - just in a slightly different pattern.

In this pic the Tank has Hover and collision 1, while the wandigo has Foot and collision 0. I cannot see much if any different in their curving behavior.
Horizontal works better than vertical for both, but in any direction both start to curve on longer distances (as illustrated by trackmarks/footsteps)

Please provide a testmap with 2 units, one curving and one definitely not curving, because as it stands this is still useless.

Aniki · Jul 22, 2016

It seems that adding a small term (-1.0, -0.01, etc) to the x component of the destination location fixes this?

JASS:

struct Loc
    real x
    real y

    static method from takes unit u returns thistype
        local thistype this = thistype.allocate()
        set this.x = GetUnitX(u)
        set this.y = GetUnitY(u)
        return this
    endmethod

    method angle_to takes Loc other returns real
        return Atan2(other.y - this.y, other.x - this.x) * bj_RADTODEG
    endmethod
endstruct

struct Path
    Loc start
    Loc end
    real direction // degrees

    static method new takes Loc start, Loc end returns thistype
        local thistype this = thistype.allocate()
        set this.start = start
        set this.end = end
        set this.direction = start.angle_to(end)
        return this
    endmethod

    method spawn takes integer uid returns boolean
        local unit u = CreateUnit(Player(0), uid, this.start.x, this.start.y, this.direction)
        if u == null then
            return false
        endif

        // call IssuePointOrder(u, "move", this.end.x, this.end.y)

        // =) ???
        // call IssuePointOrder(u, "smart", this.end.x - 1.0, this.end.y)
        call IssuePointOrder(u, "move", this.end.x - 0.01, this.end.y)

        set u = null
        return true
    endmethod
endstruct

Zwiebelchen · Jul 22, 2016

I don't think there is any reliable way to fix this, since this is directly part of how the pathfinding AI works.

The only real "fix" would be coding your own pathing algorithm and moving all units via SetUnitX/Y periodically.

Frotty · Jul 26, 2016

Aniki said:
It seems that adding a small term (-1.0, -0.01, etc) to the x component of the destination location fixes this?

Are you a little stupid or a lottle?

Zwiebelchen said:
I don't think there is any reliable way to fix this, since this is directly part of how the pathfinding AI works.

The only real "fix" would be coding your own pathing algorithm and moving all units via SetUnitX/Y periodically.

Well I can think of others, e.g. splitting up the path into segments that dont curve and then order the creep along via timer.

But if it were a simple ObjectData fix, that would be way more convenient.

Aniki · Jul 26, 2016

It seems that adding a small term (-1.0, -0.01, etc) to the x component of the destination location fixes this?

Are you a little stupid or a lottle?

It seems to work for the example in the unit-pathfinding-curving.w3x map that's attached to the post.

Frotty · Jan 27, 2017

Aniki said:
It seems to work for the example in the unit-pathfinding-curving.w3x map that's attached to the post.

No, and if you would have tested the map properly you would know that.
It works on small distances and with his specific setup, but you can produce curving by simply moving the blue circles into the corners,
or making the map bigger and moving them outwards.

Hence the question - because it should be obvious that units and orders might have arbitrary values in normal gameplay anyway. Why would adding some value change this.

as muzzel said there is no reliable way.

Aniki · Jan 27, 2017

but you can produce curving by simply moving the blue circles into the corners,
or making the map bigger and moving them outwards.

Ah, yeah I see... this is rather funny =). I tried it in melee gameplay and it does happen although I can't say I have ever noticed it before because one usually moves their units at small distances (1 screen or less) or larger distances but the map usually has obstacles that units naturally go around so its hard to notice.

I guess a workaround would be to add more points to the path that are between the start and end points of each segment because this curving seems to occur/is noticeable when the path segment is "longish".

Frotty · Jan 29, 2017

Yes, but that would be unreliable or imperformant and probably produce bad behavior due to pathing.
Anyways thanks for your response even though mine was very late ;D