Couldn't you get the angle between the two entities? Using ATan2.
You would need to disregard the Z axis and just use the Y and X co-ords. The only problem i could see there is if your ship rotates on the X axis. Then you would need to translate the other objects co-ords into the ships co-ords. That shouldn't be too hard tho :o) When you have this angle, simple rotate the arrow to that angle and your sorted :o)
You would need to disregard the Z axis and just use the Y and X co-ords. The only problem i could see there is if your ship rotates on the X axis. Then you would need to translate the other objects co-ords into the ships co-ords. That shouldn't be too hard tho :o) When you have this angle, simple rotate the arrow to that angle and your sorted :o)