colliding with STI collision maps with bump.lua?

[sam]

hi! i was wondering how i would go about making my player collide with STI-loaded collision maps utilizing bump.lua.

i can load in a map (draw it, update it, the whole thing) and i can collide my player with predefined rectangles with bump, but i'm not sure how to go about combining the two.

beginning of main.lua (i'll update this post with the .love file if it's requested). sorry for the messy code!

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local bump = require 'libs/bump'
local sti = require 'libs/sti'

require 'player'

local world = bump.newWorld(32) --new world with 32x32 tiles

local block = {name = "block",        --this is the predefined rectangle i was talking about
			   x = 64,
			   y = 64,
			   w = 128,
			   h = 128			
			  }

function love.load()
	map = sti.new('maps/map1')
    collision = map:getCollisionMap("solids") --the collision map i would like to collide with

    player_load()

    world:add(p, p.x, p.y, p.w, p.h) --player hitbox and stuff
    world:add(block, block.x, block.y, block.w, block.h) --adding in the rectangle's hitbox
end

collision code (messier!)

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if p.dx ~= 0 or p.dy ~= 0 then
		
		local future_l, future_t = p.x + p.dx, p.y + p.dy
		local cols, len = world:check(p, future_l, future_t)

		if len == 0 then
			p.x, p.y = future_l, future_t
			world:move(p, future_l, future_t)
		else
			local col, tl, tt, sl, st

			while len > 0 do
				col = cols[1]


				if col.other.name == "block" then
					tl,tt,_,_,sl,st = col:getSlide()
					p.x, p.y = tl, tt
					world:move(p, tl, tt)
					cols, len = world:check(p, sl, st)
				end


				if len == 0 then
					p.x, p.y = sl, st
					world:move(p, sl, st)
				end
			end
		end
	end

the part i'm stuck on is writing world:check() for the collision map. if anyone has any pointers, that would be great!

[kikito]

Hi, I am not familliar with STI, but the bump.lua part of your code looks alright.

the part i'm stuck on is writing world:check() for the collision map

I don't know what 'map:getCollisionMap("solids")' returns. The documentation says it's "A binary collision map". Not clear enough :/ . The way to do the collisions depends on the way this map is returned.

Can you use inspect.lua to see what's inside? Download the inspect.lua file to your lib folder, and then:

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local bump = require 'libs.bump'
local sti = require 'libs.sti'
local inspect = require 'libs.inspect' -- new line

function love.load()
   map = sti.new('maps/map1')
   local collision = map:getCollisionMap("solids") --the collision map i would like to collide with
   print(inspect(collision)) -- new line

   ...
end

That should print the contents of the collision map on the terminal.

[sam]

upon inspecting the collision map, i get this- a bunch of data relating to my solids layer.



hope this is compatible!

[kikito]

Hi there!

At the end I just gave a look at STI's source code. Taking Map:drawCollisionMap as a base, here's how you would create the necessary blocks into your empty bump.lua world (this assumes that your world is "ortogonal", not "isometric" or "staggered")

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local function createBlock(world, x, y, tileWidth, tileHeight)
  local l, t = (x - 1) * tileWidth, (y - 1) * tileHeight
  local block = { name = "block", x = x, y = y } -- , l = l, t = t, w = tileWidth, h = tileHeight --> add these if you want
  world.add(block, l,t, tileWidth, tileHeight)
  return block
end

local function createBlocksFromCollisionMap(world, collisionMap, tileWidth, tileHeight)
  local collisionData = collisionMap.collision
  local rows = #collisionData
  local cols = #collisionData[1]
  local blocks = {}
  for x=1,cols do
    for y=1,rows do
      if collisionData[y][x] == 1 then
        local block = createBlock(world, x, y, tileWidth, tileHeight)
        blocks[#blocks + 1] = block
      end
    end
  end
  return blocks
end

The usage would be:

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function love.load()
   map = sti.new('maps/map1')
   local collisionMap = map:getCollisionMap("solids") --the collision map i would like to collide with
   blocks = createBlocksFromCollisionMap(world, collisionMap, map.tilewidth, map.tileheight)

   ...
end

It is important to store the blocks in a variable which doesn't get garbage-collected (I've used a global variable called blocks here; it should probably be stored in the same place where you store the reference to your player, for example).

Disclaimer: I have written this code completely from the top of my head, no testing. Expect syntax errors/bugs. But it should give you the right direction.

[sam]

thanks for the solution! the only problem i'm having now is that this code -

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local function createBlock(world, x, y, tileWidth, tileHeight)
  local l, t = (x - 1) * tileWidth, (y - 1) * tileHeight
  local block = { name = "block", x = x, y = y } -- , l = l, t = t, w = tileWidth, h = tileHeight --> add these if you want
  world.add(block, l,t, tileWidth, tileHeight)
  return block
end

heeds this error -



i couldn't think of what went wrong here (i'm still getting used to lua syntax, haven't used it in a while). i'm not entirely sure how rect is defined, though.

[kikito]

I wrote world.add instead of world:add. Please try changing that.

[sam]

ah, that worked! guess i need to look a little harder from time to time.

thanks for all the help! my only other concern is deleting the blocks that i create. would i make another function similar to createBlocksFromCollisionMap for deleting the blocks?

[kikito]

hm, you should have told me that you planned to be able to remove the blocks in advance.

First thing you need is to change the way the blocks variable stores blocks.

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local function createBlocksFromCollisionMap(world, collisionMap, tileWidth, tileHeight)
  local collisionData = collisionMap.collision
  local rows = #collisionData
  local cols = #collisionData[1]
  local blocks = {}
  for x=1,cols do
    for y=1,rows do
      if collisionData[y][x] == 1 then
        local block = createBlock(world, x, y, tileWidth, tileHeight)
        blocks[block] = true --> this line is different now
      end
    end
  end
  return blocks
end

Then, when you have identified a particular block that you want removed (for example in a collision, it will be collision.other), you can remove it from the blocks table and from the world like this:

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function removeBlock(block, blocks, world)
  blocks[block] = nil
  world:remove(block)
end

You will probably also need to do something with STI to change the graphic of the map cell. I have no idea about that part.

[sam]

awesome, man. this solved a lot of my problems. thanks again for taking the time to write out all this code!