dariusdan's 8-dir movement

Tue, 26 May 2020 00:38:11 UTC

dariusdans8dirmove

by dariusdan

[Click to Play]

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.

Frame rate duration constancy

Sun, 25 Mar 2018 21:25:37 UTC

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

The thing is, I recorded the beeps and I noticed (using audacity) that the times of the beats are not always the same. It differs a little bit. Can frames take slightly longer or shorter times to occur inside PICO-8?

dariusdan [Lexaloffle Blog Feed]

dariusdan's 8-dir movement

Frame rate duration constancy