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dariusdan

Cart #dariusdans8dirmove-1 | 2020-05-27 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA
15

This is my code snippet for 8-dir movement in PICO-8. There are some in BBS like this but I think I have something to add here because:

1 - It doesn't move faster when going diagonals;
2 - It can move at speeds below 1 pixel/frame (sub-pixel movement);
3 - And most importantly: IT DOESN'T HAVE ANY ANNOYING JITTERING (the staircase effect)!!!

Feel free to scrutinize my code and give me any constructive tips. I am still getting started with PICO-8 and Lua.

15
10 comments




Do anyone know how constant is the duration of a frame in PICO-8?

I am considering making samething that will use rhythm and decided to use the frames as a time basis. First thing I implemented was a simple metronome.

Code below:

This function rounds a number n to the nearest integer that is multiple of m:

 
function round_mult(n, m)
 -- n is the number to be 
 --  rounded.
 -- m is the integer 
 --  significance.
 -- returns the nearest 
 --  multiple of m.

 if (n % m) == 0 then

 	return n

 else

  v_up = flr(n) + 1
  v_up = n + (m - n % m)

  v_dn = flr(n)
  v_dn = n - (n % m)

  if (v_up - n) <= (n - v_dn) then
  	return v_up
  else
  	return v_dn
  end

 end

end

On the metronome itself, I want to put a bpm and use the nearest bpm that can fit inside a frame time.

 
function _init()
	bpm = 50 -- this is not necessarily the actual bpm ingame.
	btime = 60/bpm -- time per beat in seconds
	subdivs = 4 -- subdivisions of a beat

	fps = stat(7) -- framerate
	ftime = 1/fps -- time per frame

	bframes = round_mult(
	 btime / ftime, 
	 subdivs) -- the actual bpm to be used, but in frames instead of seconds

	curframe = 1 -- frame count starts at 1
end

function _update()
	if curframe == bframes then
		sfx(1) -- this is the end of a beat
		curframe = 1
	elseif (curframe 
	 % (bframes / subdivs)) 
	 == 0 then
	 sfx(0) -- this is a subdivision of a beat
	 curframe = curframe + 1
	else
	 curframe = curframe + 1
	end
end

function _draw()
	cls()
	print(tostr(curframe))
end

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7 comments