FlxTilemap.ray() diagonal line of sight problem

[Bojer Bojington]

I have an issue with enemies being able to see my player through walls arranged in a 45-degree angle.  I am using the checkEnemyVision() function provided in part VIII of the tutorial (_mWalls.ray(e.getMidpoint(), _player.getMidpoint())).  An example of what I am talking about is shown below, more info can be found here.

I have no idea how I would make the adjustment noted in the previous link.  I would figure you make it to the ray() function, but I can't really make sense of it.  I tried to just have additional rays to check an endpoint slightly offset from the enemy midpoint, but this did not work either.  I also found something that sounded related on this thread, but making that change to my FlxTilemap class did not make a difference.  I also tried copying the latest ray function from the FlxTilemap class in the dev branch over to my local copy, but that did not make a difference either.  What am I doing wrong and how can I resolve this issue?

[Jeru Sanders]

Mm, this is kinda a problem intrinsic to raycasting, raycasting works by moving X distance in a certain direction and testing if there's a wall there, then just looping until a target is found, so this problem will occur.

You can however filter the raycast and check if it is actually valid, my idea would be something like this.

var step:Int = tileWidth;
var p:FlxPoint = FlxPoint.get();
var t:FlxPoint = FlxPoint.get();

p.copyFrom(startPoint);


for (i in 0...Std.int(distance/step)) {
    p.x += step * cos(angle);
    p.y += step * sin(angle);
    t.x = Math.round(p.x/tileWidth);
    t.y = Math.round(p.y/tileHeight);

    if (isTile(t.x + 1, t.y + 1) || isTile(t.x - 1, t.y - 1)) {
        trace("The line probably only goes from $startPoint till $p");
        break;
    }
}
p.put();
t.put();

Obviously untest, but just step through the ray result and check if this instance has occurred.

And now that I think about it I'm surprised this is how FlxTilemap().ray() is implemented. There has to be a way to properly ray cast through a tilemap rather than this step and check method.

[Bojer Bojington]

I see... that makes things clearer.  Thanks for the help, I will see what I can do :-)

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