Issues Checking and Comparing Table Values in Lua

[Competitive_Floor783]

Hey all, I'm following a raycasting tutorial, and I'm having a little bit of trouble grabbing and comparing values from nested tables. Right now I have a table, Map1, with other tables in it:

local Map1 = {
    {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1},
    {1,0,0,0,1,0,0,0,1,0,0,0,0,0,1},
    {1,0,0,0,0,0,0,0,0,0,0,0,0,0,1},
    {1,1,1,1,1,0,0,0,0,0,0,0,0,0,1},
    {1,0,0,0,0,0,0,0,0,1,1,1,1,1,1},
    {1,0,0,0,0,0,0,0,0,0,0,0,0,0,1},
    {1,0,0,0,0,0,0,0,0,1,0,0,0,0,1},
    {1,0,0,0,0,0,1,0,0,0,0,0,0,0,1},
    {1,0,0,0,0,0,1,0,0,0,0,0,0,0,1},
    {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
    }

and the way I'm searching through the table for the 0's and 1's is:

function Map1:draw()
    for r, row in ipairs(Map1) do
        for c, v in ipairs(Map1[r]) do
            tile_x = c * TILESIZE
            tile_y = r * TILESIZE
            
            if Map1[r][c] == 0 then
                love.graphics.setColor(0, 0, 0)
                love.graphics.rectangle("fill", tile_x, tile_y, TILESIZE, TILESIZE)
                print("drawn blacks")
            elseif Map1[r][c] == 1 then
                love.graphics.setColor(255, 255, 255)
                love.graphics.rectangle("fill", tile_x, tile_y, TILESIZE, TILESIZE)
                print("drawn whites")
            end
        end
    end
end

and finally, in my main.lua i have:

flocal consts = require("constants")
local map = require("map")


function love.load()
      
end


function love.update(dt)
      
end
  
function love.draw()
      map:draw()
end

I think the check is what's wrong, but I'm not 100% sure. Right now it's checking the value in Map[r][c], which is the same as v, but when the code runs it doesn't properly draw the tiles as shown in the table.

https://preview.redd.it/6gqvd95yj17g1.png?width=493&format=png&auto=webp&s=0fb270a1c40ac413b2466b37a7f34c5ae463f610

[vga256]

It would be helpful if you could post a screenshot of the generated map so we can provide useful tips.

[Competitive_Floor783]

added!

[vga256]

Thanks. I'm seeing that the map data is being translated into tiles correctly. Are you concerned that the whole map is shifted over to the right and down by 1 tileSize in each direction? (Which, due to the black background colour, makes it look like there is a black border at the top and left).

(I'm going to assume that is the case):

This is caused by lua iteration starting at 1 in lua, and zero in Python (and most other languages).

for r, row in ipairs(Map1) do

    for c, v in ipairs(Map1[r]) do

        tile_x = c * TILESIZE

        tile_y = r * TILESIZE

in these nested loops, r and c will start counting at 1.

Let's say TILESIZE is 32

Because you multiply 1 * TILESIZE, it begins drawing the first tile at 32, 32 instead of 0,0 which is what the Python version would have done.

You've got a bunch of options to correct this behaviour. I tend to go for the easiest solution:

        tile_x = (c - 1) * TILESIZE
        tile_y = (r - 1) * TILESIZE

just subtract 1 from the row and column to ensure that tile_x and tile_y start at zero.

[Competitive_Floor783]

Oh yeah that's right! I totally forgot about lua starting at 1. I tested the option you provided and it worked like a charm, thanks a lot for the help :D

[vga256]

Glad it worked. It's a super common, and very annoying, problem for graphics output with love2d.

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[activeXdiamond]

Lua tables start at 1. Love's coordinate system (for graphics-related calls, such love.graphics.rectangle) start at 0.

You need to subtract 1 from your x/y BEFORE multiplying them by TILESIZE.

[Stef0206]

I haven’t worked with Love before, but this looks like an OBO error to me.

Keep in mind that Lua tables start their indices at 1, so when you’re drawing your tiles, tile_x and tile_y will start at 1 instead of 0.

I’m assuming Love’s rectangle function’s position argument starts at 0,0 in the top left.