How to make a trigger with Ballista

How to make a trigger so that the Ballista model can shoot giant wooden arrows instead of those glaives?

Sorry to burst your bubble, but you don't need any triggers for that.

Moved to General Development.

Just change the
Combat - Attack 1 - Projectile Art
on the ballista in the object editor to desired model.

In his defense, it's not the easiest question. In RoC, the ballistas shot huge bolts. In TFT ballistas were swapped for glaive throwers and they began to shoot glaives. The model is the same path for the ballista itself (differentiated by the RoC or TFT tags in the object editor) but the projectile is a different path. Since the ballista bolt became unused with the decline of the traditional night elf ballista, it's not actually selectable from any model list in the object editor.

However, it's there. I don't know the path offhand, but you could get it by:
A) loading a RoC map with the ballistas in your WE and finding the path to the projectile
B) using War3Viewer to browse through the models in the war3.mpq until you find it
C) installing RoC and copying the path from the ballista projectile in WE
D) searching the internet for "RoC ballista projectile path"

alot of work just for 1 little model lol.

Dont you just pick your model in the object editor then choose roc or tft?

the balistas projectile was removed from the model list with the advent of frozen throne. twas replaced wit a glave. (the model is still there, just not in the list of models the editor gives)

with the balista itself, then yes. its that simple.

Just look in the mpq I know its there, as with the ballista bolt model.

Abilities\Weapons\BallistaMissile\BallistaMissile.mdx
Abilities\Weapons\BallistaMissile\BallistaImpact.mdx
Abilities\Weapons\BallistaMissile\BallistaMissileTarget.mdx

taken from war3.mpq

Minus the weird spaces of course. The forum seems to add those in for some reason.

yea... thats odd, cause when i edit my post, there are no spaces 0.o