In almost any game you will need to calculate distance between two objects.
Let’s do it.
Ok, distance^2 = delta_x^2+delta_y^2
delta_x = object2.x-object1.x
delta_y = object2.y-object1.y
Result:
1 | distance = math.sqrt((object2.x-object1.x)^2+(object2.y-object1.y)^2) |
Sample of usage:
Code:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 | -- calculate distance between o1 and o2 function distance(o1,o2) return math.sqrt((o1.x-o2.x)^2+(o1.y-o2.y)^2) end -- check is point(p) in rect(r) function is_in_rect(p, r) if p.x>=r[1] and p.x=r[2] and p.y return true end return false end -- hide status bar display.setStatusBar( display.HiddenStatusBar ) -- fill background local bg = display.newRect(0,0, display.contentWidth, display.contentHeight) bg:setFillColor(160, 230, 255) -- create two objects local object1 = display.newRect(100,100, 10,10) local object2 = display.newRect(200,200, 10,10) -- line between objectslocal local line -- distance label local distance_lbl = display.newText("", 300,10, native.systemFont, 14) distance_lbl:setTextColor(0,0,0) -- run this function on touch local function move_object(event) local o1, o2 = object1, object2 local ro1 = {o1.x-o1.width/2, o1.y-o1.height/2, o1.x+o1.width/2, o1.y+o1.height/2} local ro2 = {o2.x-o2.width/2, o2.y-o2.height/2, o2.x+o2.width/2, o2.y+o2.height/2} if event.phase=="began" then -- just began - check which object is touched and mark it if is_in_rect(event, ro1) then object1.moving = true elseif is_in_rect(event, ro2) then object2.moving = true end elseif event.phase=="moved" then -- moving - move touched object if object1.moving then object1.x, object1.y = event.x, event.y elseif object2.moving then object2.x, object2.y = event.x, event.y end elseif event.phase=="ended" then -- end - mark both objects as untouched object1.moving, object2.moving = false, false end end Runtime:addEventListener("touch", move_object) -- calculate distance between objects and update distance label every 1/30 second local function main_loop() distance_lbl.text = distance(object1, object2) if line then line:removeSelf() end line = display.newLine(object1.x, object1.y, object2.x, object2.y) end Runtime:addEventListener("enterFrame", main_loop) |
Just wanted to let you know of an issue on line 8….
if p.x>=r[1] and p.x>=r[2] and p.y then return true
is how it should read….
Other than that it’s great thanks!!!!