Legacy GM "distance_to_object" giving incorrect/inconsistent results

[Dieter]

I'm pretty new to programming and gamemaker so I might be missing something very obvious here. I'm working on a small game and one of the spells is a ray of heat (like in Diablo). The beam shouldn't go through walls so I wrote some code that adjusts the size of the beam when it's hitting a wall. Sometimes it works correctly (although the beam flickers) but sometimes it becomes way to short. Through show_debug_message I noticed the problem: distance_to_object gives an incorrect distance. In the added screenshot you can see that it returns a value of 71 pixels, while the actual distance to the wall is 139px (I checked).

Does anyone have a clue what's going on here? The funny thing is, other collisions with the wall work pixel perfect (other spells, the player, etc).

Many thanks in advance!

var ratio
var instwall
instwall = collision_line(x, y, x + beamendx, y + beamendy, obj_wall, false, true){
    if instwall != noone{
        ratio = distance_to_object(instwall) / lengthofbeam;
        image_xscale = ratio; 
        show_debug_message("ratio is" + string(ratio));
        show_debug_message("distance to wall is" + string(distance_to_object(instwall)))
    } else {
        image_xscale = 1;
    }
}

 

[NightFrost]

What is throwing you off is, distance_to_object() measures distance between bounding box edges, not x/y points.

 

[Dieter]

Thanks for your reply NightFrost, but I don't think that's it. The bounding box should be overlapping with the sprite of the wall. As you see on the screenshot, the collision is happening a couple of grids before the actual wall and its bounding box. Please correct me if I'm wrong though.

 

[Dieter]

Aha! I thought about it some more and realized the beam sprite also has a bounding box. I'm guessing that's what you meant. Since these all these bounding boxes made calculations quite unpredictable I searched for alternative functions and found that gamemaker also has a function "point_distance(x1, y1, x2, y2)". Which solved the problem. Thanks again!