Quick Links: Download Gideros Studio | Gideros Documentation | Gideros community chat | DONATE
Movement AI question, suggestion needed — Gideros Forum
  • Home
    • ›

    Movement AI question, suggestion needed

    piepie Member
    edited December 2018 in Game & application design
    Hi,
    I am asking for help on a logical/math issue I've stumbled upon: this is part of the AI that should move the enemy horde in a tower defence game.
    I know the locations of the waypoints were the enemies should go

    waypoints = {{x,y}, {x2,y2}, {x3,y3}...}

    and I've got 3 skill levels on each enemy type, meaning that enemy at skill level 1 uses enemy.speed[1], level 2 enemy.speed[2]...

    enemy.speed = {0.5,0.7,1}


    this is pseudocode for the enterframe function that moves them, and worked perfectly until I decided to use decimal numbers in my speed tables; but it won't work if I don't reach integer coordinates, equal to my waypoint coordinates.
    function onEnterFrame()
 
	--This is the "check" I need to change: using decimal numbers getX() won't ever reach integer coordinates, unless I use only 0.2 and 0.5...
	if enemy:getX() == waypoint.x and enemy:getY() == waypoint.y then
		set next waypoint
 
	elseif enemy:getX()waypoint.x then
		enemy:setX() = enemy:getX() - enemy.speed[enemyskill]
 
	...the same applies with Y position...
	end
 
end
    The issue is that I'd like to use decimal numbers to differentiate speeds (there is already too much gap between 1 and 2 pixels per frame) but I need to find a better check to perform, to understand when they need to change waypoint.
    Any suggestion for a math trick or a different approach?

    Thank you
    +1 -1Share on Facebook

    Comments

    • hgy29hgy29 Maintainer
      edited December 2018
      Why not using a distance check (or better: a squared distance check): if your enemy is within 1px range of the waypoint, then assume it has reached the waypoint.
      +1 -1Share on Facebook
    • piepie Member
      @hgy29 I think I will follow your suggestion: can you elaborate a bit on the "squared distance check" please? :)
      My horde to keep things simple just move on one axis at a time, and the waypoints are "aligned" (same X or same Y between them)

      Thank you
      +1 -1Share on Facebook
    • piepie Member
      Did you mean this one?

      If (x,y) is the centre of the rectangle, the squared distance from a point (px,py) to the rectangle's border can be computed this way:
      dx = max(abs(px - x) - width / 2, 0);
dy = max(abs(py - y) - height / 2, 0);
return dx * dx + dy * dy;
      If that squared distance is zero, it means the point touches or is inside the rectangle.

      source: https://gamedev.stackexchange.com/questions/44483/how-do-i-calculate-distance-between-a-point-and-an-axis-aligned-rectangle
      +1 -1Share on Facebook
    • hgy29hgy29 Maintainer
      I mean just don’t bother using sqrt to get the true distance, you can compare with the squared value on each side of the < or >

      Likes: pie

      +1 -1 (+1 / -0 )Share on Facebook
    • SinisterSoftSinisterSoft Maintainer
      @pie you can use <> for max and >< for min rather than call a math lib function - they should be slightly faster.
      Coder, video game industry veteran (since the '80s, ❤'s assembler), arrested - never convicted hacker (in the '90s), dad of five, he/him (if that even matters!).
      https://deluxepixel.com
      +1 -1Share on Facebook
    • SinisterSoftSinisterSoft Maintainer
      https://wiki.giderosmobile.com/index.php/Larger_and_Smaller_Operators
      Coder, video game industry veteran (since the '80s, ❤'s assembler), arrested - never convicted hacker (in the '90s), dad of five, he/him (if that even matters!).
      https://deluxepixel.com
      +1 -1Share on Facebook
    • piepie Member
      Thank you @SinisterSoft I did it: the fastest route was to adapt the example to check if the value is inside boundaries, and it is pretty fast! since it's an enterframe call everywhere I could save is really good :)
      +1 -1Share on Facebook
    Sign In or Register to comment.