Hello again! Future me here to say, I probably should have used a better word than scan. But to give you the high level gist, if your terrain doesn’t change, you can project your projectiles path, and then just move it along the path if no issue.
This requires knowing how your projectile it going to move. If it’s only going forward, you just project a straight line until it makes a collision, then plot a point X units above that, and then continue projecting forward from there. I’ll do a bit of a visual mockup, let me know if it makes sense.
Red: Trace forward until a hit or for fixed distance, then poll downward if no hit, poll upward if hit, then capture that location for the next trace location and a spline point. After that it repeats the same and makes a spline point every fixed distance. Then when all the projection is done, a spline is generated from those points and that should be much cheaper, but you’ll have to set up the projection beforehand.
If your game is closer to how MOBAs function this can be even less accurate because the hitboxing is 2 dimensional.