Creating boundaries and collisions?

[crystalheartstudios]

Alright so I am trying to make a top down zelda/pokemon-esque game using tiles. Now I need to prevent my character from walking out of the map, as well as I am attempting to prevent him from passing through props like trees, chests, structures, etc. Can somebody please explain the simplest way to do this, along with any resources that may allow me to do this? Thanks in advance!

[HugoBDesigner]

The easiest for you would be using a physics library, like Bump, for example. I also have a physics engine I've just finished working on and may release really soon. Making a physics engine is a bit hard and takes a bunch of time. If it is okay for you to use a library, just try searching a few here in the forums (or using the one I linked). You can also use Löve's built-in physics system from [wiki]love.physics[/wiki], but it is a bit more complicated than you actually need (although it still works, of course). Lastly, you can private message me and I will help you however I can

[Zilarrezko]

yeah, you could do what Hugo Said, and go the library route. But it looks like what you're using is simple enough.

I can go the code way of explaining it, or the paragraph way. I'll go with the code way since writing a paragraph will likely confuse people more. I'll assume you want it pretty much exactly like the first zelda game, and the first pokemon games.

Code: Select all

function love.load()
   player = {}                               --Make out player and all that
   playerImage = love.graphics.newImage("graphics/player.png") --Here we load the players image from the graphics folder (if u put it here)
   player.x, player.y, player.w, player.h = 0, 0, playerImage:getDimensions()             --make the player at 0, 0 with image's width & height
   player.xCollision = false                 --We'll use these to see if the player tried to run into a tree
   objects = {}                             --have a table to hold objects.
   objects[1] = {x = 100, y = 100, w = 50, h = 50, t = "tree", walkable = false}                         --Create the first object, let's make it a tree
   treeImage = love.graphics.newImage("graphics/tree.png") --Here we load the tree image, that we have in the graphics folder.

   function boxCollision(x1, y1, w1, h1, x2, y2, w2, h2)                                  --to see if one box, is inside another box.
	return y1 < y2 + h2 and y2 < y1 + h1 and x1 < x2 + w2 and x2 < x1 + w1
   end

end

function love.update(dt)
   if love.keyboard.isDown("s") then -- If the s key is down, then continue (this is checked every frame)

      for i = 1, #objects do                --iterate through every object in the objects table
         if boxCollision(player.x, player.y + dt, player.w, player.h, objects[i].x, objects[i].y, objects[i].w, objects[i].h) and not walkable then
             player.collision = true  --I'll explain this after
             break
         end
      end
      if not player.collision then
          player.y = player.y + dt
      end
      player.collision = false

   elseif love.keyboard.isDown("w") then

      for i = 1, #objects do
         if boxCollision(player.x, player.y - dt, player.w, player.h, objects[i].x, objects[i].y, objects[i].w, objects[i].h) and not walkable then
             player.collision = true
             break
         end
      end
      if not player.collision then
          player.y = player.y - dt
      end
      player.collision = false

   elseif love.keyboard.isDown("a") then

      for i = 1, #objects do
         if boxCollision(player.x - dt, player.y, player.w, player.h, objects[i].x, objects[i].y, objects[i].w, objects[i].h) and not walkable then
             player.collision = true
             break
         end
      end
      if not player.collision then
          player.x = player.x - dt
      end
      player.collision = false

   elseif love.keyboard.isDown("d") then

      for i = 1, #objects do
         if boxCollision(player.x + dt, player.y, player.w, player.h, objects[i].x, objects[i].y, objects[i].w, objects[i].h) and not walkable then
             player.collision = true
             break
         end
      end
      if not player.collision then
          player.x = player.x + dt
      end
      player.collision = false
   end

end

function love.draw()
    for i = 1, #objects do
       if objects[1].t == "tree" then
          love.graphics.draw(treeImage, object[1].x, object[1].y)
       elseif object[1].t == "whateverelse" then
      
       end
    end
    love.graphics.draw(playerImage, player.x, player.y)
end

Alright, I haven't tested it, but read it over a few times and you'll maybe, just maybe, get the logic.

so for this block of code here:

Code: Select all

for i = 1, #objects do
         if boxCollision(player.x, player.y + dt, player.w, player.h, objects[i].x, objects[i].y, objects[i].w, objects[i].h) and not walkable then
             player.collision = true
             break
         end
      end
      if not player.collision then
          player.y = player.y + dt
      end
      player.collision = false

what it's doing is going through every object in the object table, then testing to see if the player, with the the added dt (time in between frames) is inside of another box (we haven't moved the player yet.). if the player with the added dt is inside of another tile, then it checks to see if the tile is walkable. If it isn't, than a collision happened. Then we do a check to see if the collision didn't happen, and then adds (or subtracts based on where we want the player to move) the dt to the players coordinates.

This is the most basic of collision testing. Although, to beginners (even when I started out) Concepts are the hardest to grasp. Especially if you have trouble with the coding language you're writting in. Or you may be very good in Lua, in which case this code will be easy to read. In any case, I'll be here, ready to answer questions, as will the rest of the great community.

[Rockford]

Zilarrezko you are awesome. I have been spending the last few weeks learning about tile collision and such
and keep hearing (well seeing) people on here talking about checking for collision BEFORE moving the player,
and I never understood it. Now I do thanks to your code and post!

Thanks

[Zilarrezko]

Zilarrezko you are awesome. I have been spending the last few weeks learning about tile collision and such
and keep hearing (well seeing) people on here talking about checking for collision BEFORE moving the player,
and I never understood it. Now I do thanks to your code and post!

Thanks

Very happy to help man Have a good one!