Unit Replacement

[The Arcot]

Hullo thar everyone. I recently resumed work on a builder map I've been working on, and it's finally starting to take shape. However, I've recently run into a minor problem.

Basically what i want to do is make a structure that is capable of transforming certain units, namely the Orc Grunt into a Fel Orc Grunt, Raider into Fel Orc Raider etc. However, this does not include ALL orc units, only three or four.
Also, they should not be able to change back into the regular non-fel versions.

What I figured I would do is make simple targeted spell, such as Holy Light, and edit it so it has no animation and does nothing, and then trigger that if the target is a specific unit type, it would replace that unit with the appropriate 'corrupted' version.

I think the only problem I'm having is the event. I can never remember the differences between the events such as "A unit begins casting an ability/begins the effect of an ability/ends the effect" etc.

In short, which do I use? If possible, a full piece of code as an example for one conversion would be ideal, thanks

Also, sorry if this post is too long for such a simple question. It's a failing of mine.

 

[ThePlague]

Beings casting checks before cooldown is actually fired
starts the effect checks before actualy ability goes but after cd is fired

In this case you could just use the ability Sacrifice (the one sacrificial pits have) and avoid triggers all together

 

[The Arcot]

Don't both the unit and the structure both have to have the ability sacrifice for it to work? I'm trying to make the system as unobtrusive as possible.

And it's a building that would be casting the ability, and there would probably be no cooldown, or at most a very short one, so which would work better (seem and look smoother): Begin casting or start the effect?

 

[FireBladesX]

In your case, begin would be adequate, but I think 95% of the time, starts the effect would be better in general. For a building, they would be the same, anyways, because I think that buildings have zero casting time.

But, generally, begin is exploitable, because if you spam your stop key once you issue the order, the trigger is fired without using mana cost or cooldown. "starts the effect of an ability" waits until the mana cost and cooldown have already triggered to start your trigger.

 

[ThePlague]

you want "starts the effect" you almost always want this one
although if there is no casting time,cd, or mana cost it makes no difference

Not sure if the unit also has to have sacrifice, if it does you could stick it in an invisible spellbook

 

[TheDamien]

You want "starts an effect".