LÖVE

Code: Select all

-- nice to have locals, put them outside any function
local speed, dx, dy, o_x, o_y

function love.load(arrrrgs)
  speed = 1.0 -- seconds -- not speed, time though
  dx,dy -- how much do we need to add/subtract from the below coordinates to get to our goal position with the above speed.
  o_x, o_y = 0,0 -- object coords
end

function love.mousereleased(butt,x,y)
  -- separating axis theorem provides us blah blah blah, doing this works out just as well as converting to a polar coord sys, doing the math there, then converting back (since we need the delta amounts separated anyway)... unless i'm wrong, of course :3
  dx = (o_x - x) / speed
  dy = (o_y - y) / speed
end

function love.update(dt)
  o_x = o_x + dx * dt
  o_y = o_y + dy * dt
end

Code: Select all

local speed = 100 -- desired speed in pixels/s

local obj_x, obj_y = 400, 300
local obj_vx, obj_vy = 0, 0

local pos_at_click_x, pos_at_click_y = obj_x, obj_y
local target_x, target_y = obj_x, obj_y
local dist_at_click2 = 0

function love.mousepressed(x, y, b)
  pos_at_click_x = obj_x
  pos_at_click_y = obj_y
  target_x = x
  target_y = y
  -- Calculate and remember the square of the distance to travel
  dist_at_click2 = (target_x - obj_x)^2 + (target_y - obj_y)^2

  -- Divide displacement vector by its length to normalize it,
  -- and multiply resulting unit vector by speed
  if dist_at_click2 == 0 then
    obj_vx, obj_vy = 0, 0 -- avoid division by 0
  else
    local dist_at_click = math.sqrt(dist_at_click2)
    obj_vx = (target_x - obj_x) / dist_at_click * speed
    obj_vy = (target_y - obj_y) / dist_at_click * speed
  end
end

function love.update(dt)
  obj_x = obj_x + obj_vx * dt
  obj_y = obj_y + obj_vy * dt

  -- Check if overshooting (we check the square of the distance to avoid
  -- calculating a square root)
  local dist = (pos_at_click_x - obj_x)^2 + (pos_at_click_y - obj_y)^2
  if dist >= dist_at_click2 then
    -- Overshot - teleport to target instead.
    obj_x = target_x
    obj_y = target_y
    obj_vx = 0
    obj_vy = 0
  end
end

function love.draw()
  love.graphics.rectangle("line", obj_x-0.5, obj_y-0.5, 3, 3)
end