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I'm attempting to create a fully-fledged platformer game with Picotron, and I'm encountering some collision detection issues. You see, I followed Nerdy Teachers' platformer collision tutorial since I figured the code would work with Picotron (it technically being an advanced PICO-8 after all). And I'm correct, but something is seriously wrong. When I tested the collision code, this is what I was presented with:

Now I think this is happening due to one or more of the following reasons:

  • The code was designed with 8x8 sprites in mind when my player character is in a 16x24 resolution and the tiles are 16x16 sprites.
  • The code wasn't made with Picotron in mind (since the Nerdy Teachers tutorial I followed predates Picotron by quite a while).
  • I've just been a complete idiot and made a mistake in the code that is causing this whole kerfuffle.

I've provided the code for the collision system and player physics below, as well as the player's table and physics variables. If anyone can help me rewrite or optimize the code to work with Picotron, then that would be a great help and I sincerely thank you for your assistance. <3

 
-- Player variables
	player={
		sp=16,
		x=20,
		y=44,
		w=16,
		h=24,
		dx=0,
		dy=0,
		max_dx=2,
		max_dy=3,
		acc=0.5,
		boost=4,
		anim=0,
		running=false,
		jumping=false,
		falling=false,
		landed=false,
		flipx=false,
		health=3,
		lives=2
	}
	-- Physics variables
	gravity=0.3
	friction=0.85
 
-- Collision system (thanks nerdy teachers :D)
function collide_map(obj,aim,flag)
	-- obj = table needs x,y,w,h
	-- aim = left,right,up,down
	local x=obj.x	
	local y=obj.y	
	local w=obj.w
	local h=obj.h

	local x1=0
	local y1=0
	local x2=0
	local y2=0

	if aim=="left" then
		x1=x-1
		y1=y
		x2=x
		y2=y+h-1
	elseif aim=="right" then
		x1=x+w
		y1=y
		x2=x+w+1
		y2=y
	elseif aim=="up" then
		x1=x+1
		y1=y-1
		x2=x+w-1
		y2=y
	elseif aim=="down" then
		x1=x
		y1=y+h
		x2=x+w
		y2=y+h
	end
	--pixels to tiles conversion
	x1/=8
	x2/=8
	y1/=8
	y2/=8

	if fget(mget(x1,y1), flag)
	or fget(mget(x1,y2), flag)
	or fget(mget(x2,y1), flag)
	or fget(mget(x2,y2), flag) then
		return true
	else
		return false
	end
end

function player_update()
	--Physics
	player.dy+=gravity
	player.dx*=friction

	--Controls
	--Moving status
	if btn(0) then
		player.dx-=player.acc
		player.running=true
		player.flipx=true
	end
	if btn(1) then
		player.dx+=player.acc
		player.running=true
		player.flipx=false
	end

	--Sliding status
	if player.running
	and not btn(0)
	and not btn(1)
	and not player.falling
	and not player.jumping then
		player.running=false
		player.sliding=true
	end

	--Jumping status
	if btnp(5) and player.landed==true then
		player.dy-=player.boost
		player.landed=false
	end

	--Check collision on the y-axis
	if player.dy>0 then
		player.falling=true
		player.landed=false
		player.jumping=true

		if collide_map(player,"down",0) then
			player.landed=true
			player.falling=false
			player.dy=0
			player.y-=(player.y+player.h)%8
		end
	elseif player.dy<0 then
		player.jumping=true
		if collide_map(player,"up",1) then
			player.dy=0
		end
	end

	--Check collision on the x-axis
	if player.dx<0 then
		if collide_map(player,"left",1) then
			player.dx=0
		end
	elseif player.dx>0 then
		if collide_map(player,"right",1) then
			player.dx=0
		end
	end

	--Stop sliding
	if player.sliding then
		if abs(player.dx)<.2
		or player.running==true then
			player.dx=0
			player.sliding=false
		end
	end

	player.x+=player.dx
	player.y+=player.dy
end

(Keep in mind that this is all Picotron code)

I'm not sure, but I think the problem is caused by the map's collision detection.

 
x1/=8
x2/=8
y1/=8
y2/=8

if fget(mget(x1,y1), flag)
or fget(mget(x1,y2), flag)
or fget(mget(x2,y1), flag)
or fget(mget(x2,y2), flag) then
return true

I can't tell from the code, but I think the map chip is not 8x8 pixels.
This is all just my speculation, but I hope it will help solve the problem.

@sugarflower is right, map tiles are 16x16 pixels (they actually take on the resolution of sprite 0, but that's 16x16 by default).



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