i wrote a tut for halo pc active scenery on hih...ill find it and paste it here in a min
EDIT:
in this example we will make a plane fly across the map
1. HMT>PROJ tag> MP_needle
2. copy meta
3.HMT>equip tag> health pack> paste needle meta
4. extrack model of turret and make it look like a plane (or w/e u want)
5. HHT> PROJ> MP_needle> at the top it will say somthin like MOD2: needle
6. dependancy swap the MOD2 for the turret (near the bottom)
7.open spark edit.
8. place health packs where u want to planes to start flying. pointing in the direction u want them to fly.
thanks for the comments
