blobs.p8.lua

-- https://twitter.com/weeble/status/1507516219313868803

function density(
 px,py,ox,oy,r,s
)
 local dx=px-ox
 local dy=py-oy
 -- Urgh d^2 overflows Pico8's
 -- 16.16bit fixed point really
 -- easily. Don't let it.
 if abs(dx)>r then
  return 0
 end
 if abs(dy)>r then
  return 0
 end
 local d2=dx*dx+dy*dy
 local r2=r*r
 if d2>r2 then
  return 0
 end
 local t=1-d2/r2
 return s*t*t
end


function _draw()
 cls(0)
 t={}
 function e(x,y)
  -- Memoise this because calling it
  -- less is hard and my brain is bad
  local idx=200*y+x
  local cached=t[idx]
  if cached!=nil then
   return cached
  end
  local d=0
  for item in all(origins) do
   d=d+density(
    x,y,item[1],item[2],item[3],item[4]
   )
  end
  t[idx]=d
  return d
 end
 function blob(x,y,size)
  if size==1 then
   local v=e(x,y)
   if v>0.5 then
    pset(x,y,1)
   end
  else
   local v1=e(x,y)
   local v2=e(x+size,y)
   local v3=e(x,y+size)
   local v4=e(x+size,y+size)
    
   if size<=8 then
    if max(max(v1,v2),max(v3,v4))<0.5 then
     return nil
    elseif min(min(v1,v2),min(v3,v4))>0.5 then
     fillp(0x0f0f)
     rectfill(x,y,x+size,y+size,2)
     fillp(0x0000)
     rect(x,y,x+size,y+size,3)
     return nil
    end
   end
   size\=2
   blob(x,y,size)
   blob(x+size,y,size)
   if size>=2 then
    blob(x,y+size,size)
    blob(x+size,y+size,size)
   end
  end
 end
 blob(0,0,128)
 --print(stat(1))
end

function _init()
 -- {x,y,radius,density}
 origins={
  {32,64,48,1},
  {96,70,48,1},
  {64,0,80,1.8}
 }
 velocities={
  {0.3,0.1},
  {-0.2,0.4},
  {0.1,-0.5}
 }
end

function up(n)
 origins[n][1]+=velocities[n][1]
 origins[n][2]+=velocities[n][2]
 local dx=origins[n][1]-64
 local dy=origins[n][2]-64
 -- Wild guess at gravity, kinda works
 -- Prolly should handle dx==dy==0
 local str=1/(dx*dx+dy*dy)
 velocities[n][1]-=dx*str
 velocities[n][2]-=dy*str
 -- Clamp to avoid escape
 origins[n][1]=mid(-200,origins[n][1],200)
 origins[n][2]=mid(-200,origins[n][2],200)
 velocities[n][1]=mid(-32,velocities[n][1],32)
 velocities[n][2]=mid(-32,velocities[n][2],32)
end

function _update60()
 up(1)
 up(2)
 up(3)
 if btn(⬆️) then
  origins[1][2]-=10
 end
 if btn(⬇️) then
  origins[1][2]+=10
 end
 if btn(⬅️) then
  origins[1][1]-=10
 end
 if btn(➡️) then
  origins[1][1]+=10
 end
end