So I previously described my "scan bullet", which I thought was a pretty interesting way to get the results I wanted, but obviously flawed. With a bit of advice from folks at NeoGAF's GameMaker thread, though, I learned of a few tricks to do it better without an actual scan bullet object. As I said there, GameMaker's help system is very nice, but it can still be trouble to find if a certain type of function actually exists if you don't know quite what to search for. In this case I learned of a few important things.
The collision_line function can take a start point and end point, and return whether there would be a collision with a certain kind of object anywhere along that line segment. The problem is, if it would collide with multiple things along that line, it seems to just return information about one of them at random. So not perfect by itself for determining what is right in front of the ship.
Lengthdir_x and lengthdir_y are used for finding points a certain pixel distance away from a point at a certain angle. So knowing where the ship is located and what its angle is, this can check for what's 1 pixel in front of it, 2 pixels in front, and so on. So it's easy enough to do a loop of this and return information on the first asteroid (if any) it comes across.
It might be the case that there would be some computational savings from doing collision_line to see if there's any collision at all, then using a lengthdir loop to make sure the closest is found... but I'm not sure how much of a savings, and for my simple project where it's only being used to check one thing probably not worth the hassle, so I'll just put collision_line back on the shelf for now.
Comments