I am trying to design a spell that, once activated, shoots 4 projectiles.
Each of them are respectively ordered to move North, West, South, East. They should accelerate over-time (start -extremely- slow and then accelerate relatively quickly to a max speed), and explode (dealing damage) on the first Stalker unit (and only Stalker!) they encounter.
Once they reach the edge of the map, they should explode.
For aesthetic purposes, I'd like each projectile to individually start offset-toward-its-direction from the caster unit

If possible, we should see them on the mini-map too.
I guess triggers are allowed, but I really would like to see this completely done via the Data module.

You can edit the projectile mover to adjust start speed, max speed, and acceleration. There's also Orientation, so you can change what direction it faces. ( I think, it could be vectors. If it's vectors, you need to use Throw, then adjust Throw Vector.)

As for exploding when they reach the end of the map, if there's a trigger for destroying projectiles, try that. Not sure about the stalker thing, or the minimap thing.

I have never made even a basic projectile/missile spell. Could you try to be more explicit about the entirety of the steps required to achieve my goal?

I'd do this through persistent effects. A Persistent can have various kinds of offsets. The "Periodic Offsets" use the local coordinate system (that is, the unit's facing angle is taken into consideration) but the others do not, to my knowledge... I know for sure that the "Final Offset" doesn't. So, create four Create Persistent effects that call Launch Missile effects as their final effects, and set the final offsets to the four directions you want.

Use a behavior that periodically (and extremely frequently) calls a Search Area effect to make them explode upon contact.

I just want to be sure before starting to work on this method:


Above should shoot like this:

---

Above should shoot like this:


What you've said would do what I want?

You don't need persistent effects since launch missile has it's own offsets. You would use 4 different launch missile effects change the impact location to change the impact location to the caster unit and change the impact offset to a large number in the direction you want (example: for a north launch you would do 0,-1000), you may need to change 1000 as you see fit.

Well, it works with Launch Missile effect of impact location "Target Unit/Point" and the offset to whatever huge number I wanted. I've also set a Launch Offset.
I made the Unit Ammo the Photo Canon missile, and I increased its scale with the Actor tab. I've also set its Minimap Radius through Actor tab as well.
The problem is the Damage effect, which doesn't seems to work.

P.S. It launches my bullet, but it passes through units without dealing any damage nor exploding.
P.S. #2: Forgot to say I tried to set a max speed, an acceleration value and a movement radius to the Photo Canon Missile unit (through Unit tab), though it didn't work.

If you want to edit the speed/movement of the missile edit the mover that the missile uses. To get the damage dealt you need to add a behaviour onto the missile with a periodic effect and a very small period time (0.01), and have it call a search effect that searches for a unit and causes a damage effect.

For the mover, how to get the acceleration to be exponential until it reaches a certain speed?
And related to what I've said, I found out the "Launch Offset" doesn't seem to work. Even with (0,20000) the missile would start from the center of the stalker. D:

Anyways, I've done what you've said, but somehow, it looks like the missile only applies damage to the caster (which kills him). When the missile passes through the enemy (why doesn't it explode?), it doesn't deal any damage... weird! Moreover, I have excluded Self and Player from the Search.
I'll attach the map so it is easier for you guys to experiment around.

P.S. I made the spell only for North since I didn't want to do superfluous actions on already-duplicated blank effects.

Attachments:

You need to change the way you are using the damage effect. You should be doing this Behaviour -> Search Effect -> Set Effect -> Damage Effect and Suicide Effect.

/me 100% lost.

So your behaviour needs to periodically call a search effect with a radius of whatever (the whole square or just the missile) which calls a set effect (just an effect that calls multiple effects). These two effects are a damage effect and a suicide effect (already in there for you).

Now as soon as I press the ability button, I explode and there isn't even a bullet coming out.
This is getting me really mad. Could anyone please do it for me and/or write a complete and -extremely- explicit Wiki ?

Resume of my current situation:

The ability is of "Behaviour" type. It calls a Behaviour of "Buff" type.
This Behaviour has an Initial Effect of type "Launch Missile" and a Periodic effect (and a Periodic value) of type "Search Area".
The Search Area effect calls a "Set" effect which calls "Damage" and "Suicide" type effects.
The Launch Missile effect has its Impact Location set to Target Unit/Point and an Offset corresponding to the direction I want it to go.

When I click the ability, the Behaviour is applied, the Missile is Launched, the caster isn't affected by the missile (which is intended), but it passes through enemies without either exploding or dealing damage.

Ok you have almost got it right I must have confused you when I talked about the behaviour earlier.

When I was saying above for the Behaviour -> Search Effect -> Set Effect -> Damage Effect and Suicide Effect this had nothing to do with launching the missile, sorry for confusing you.

Your launch should look like this Ability (Instant) -> Set Effect -> Launch Missile x4 (with different offsets for each). You seem to have had this taken care of earlier.

Now the behaviour part I was talking about is the part that controls the damage this missile does, so you do not need any impact or any other effects on the launch missile. Have the behaviour like you set it up already but remove the Launch Missile effects from it and put it on the missile unit you are launching.

I changed the ability type to "Effect - Instant" and linked my "Set" effect.
I don't understand what you mean by "Set Effect -> Launch Missile x4". You told me to put Damage and Suicide under Set, and now it should be Launch Missiles?

They are both under a (different) set. You want to launch 4 missiles at once so you will need to have 4 different effects so you will need a set effect.

Now, I can't see the projectile anymore. I think it simply explode as soon as it is launched because it is launched on the Caster. At least, now, it deals only one time the 10 damages it is supposed to deal.
What's weird is that I excluded "Caster" from the "Search Area" of the Search effect.

Exclude player from the search filter, also missile

Woooooot! It works!

-Finally-

Anyways, may I know how to pretty it up now? I'd like to run an animation on the caster when the missile is launched and actually have the same animation as the Photo Canon's missile unit explosion when the missile explodes.

EDIT: Oh wait, I'm still missing the exponential acceleration.