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I'm working on a game that notes how high players climb. Right now I'm trying to put together a "ruler" that stays on the left side of the screen and scrolls with the player, letting them know at a glance how far they've traveled. Every 50 pixels, the ruler has a slightly longer line, and a printed numerical value indicating the corresponding height. Here's what I have so far.

Cart #fozadasohu-0 | 2024-06-20 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA

Right now, the ruler is powered by a for loop in the function draw_elevation(), which means that it has a definite start and end. Could anyone recommend a method for making the ruler extend in both directions indefinitely (without crashing PICO-8)? My efforts to try while and repeat loops have failed. (Bonus points for making the 0 line start at the bottom or center of the screen!)

Here is the code as it stands, since the site's cart dropdowns aren't working right now:

--height measure

function _init()
 camx=0
 camy=0
 screen_height=128 
end

function _update()
 if btn(⬆️) then
  camy-=1
 end
 if btn(⬇️) then
  camy+=1
 end
end

function _draw()
 cls(12)
 camera(camx,camy)
 draw_elevation() 
 --debug: cam values
 print("camx: "..camx,85,camy+3,8)
 print("camy: "..camy,85,camy+10,8)
end

function draw_elevation()
 --to do: have 0 line at screen bottom (or at center with negative heights below)

 --to do: make the ruler extend indefinitely so that any height is recorded/printed

 --these values are kind of arbitrary at the moment
 for i=150,-screen_height,-10 do
  --draw measuring lines
  line(0,i,3,i,2)
  --longer line for every multiple of 50
  if i%50==0 then
   line(4,i,7,i,2)
   --label for longer line
   print(-i,10,i-2,2)
  end
 end
end
P#150169 2024-06-20 23:30 ( Edited 2024-06-21 01:58)

1

Cart #wujisezeba-0 | 2024-06-21 | Code ▽ | Embed ▽ | No License

You're almost there, but instead of displaying your ruler in the fixed 150 to -128 range, you have to adapt the starting and ending point to only display the part of the infinite ruler that is onscreen. Depending on your game, remember that valid integer coordinates can't go above 32767 or below -32768. If you need more, things get a bit more complicated.

for i=150,-screen_height,-10 do

becomes

top_tick=(camy\10)*10
for i=top_tick,top_tick+screen_height+10,10 do

top_tick is the height where to place the tick that is on or above the 1st line of the screen. By integer dividing by 10 and remultiplying by 10, you discard the unit digit, and because the Y axis goes down, your tick goes up onscreen.

For original placement of the 0 tick to the bottom of the screen, I just set camy to -127, but you usually get that kind of placement for free once the camera is tied to the player.

P#150187 2024-06-21 06:34

This is brilliant! Thank you, RealShadowCaster. I appreciate it.

P#150215 2024-06-21 16:58

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