rotutil.lua

names={"South","West","North","East","Up","Down"}
local fM={nil,3,1,2,4}
offsets={{0,0,1},{-1,0,0},{0,0,-1},{1,0,0},{0,1,0},{0,-1,0}}
opposite={3,4,1,2,6,5}
function addDir(dir,x,y,z,t)
  t=t or 1
  if not offsets[dir] then error("invalid dir",2) end
  if not (x and y and z) then error("must provide x,y,z",2) end
  local px,py,pz=unpack(offsets[dir])
  --print("x=",x," px=",px," y=",y," py=",py," z=",z," pz=",pz," t=",t)
  return x+px*t,y+py*t,z+pz*t
end
function fromMeta(meta)
  return fM[meta]
end
function rotL(dir)
  if dir<1 or dir>6 then error("invalid dir",2) end
  if dir>=5 then
    return dir
  end
  if dir == 1 then return 4 end
  return dir-1
end
function rotR(dir)
  if dir<1 or dir>6 then error("invalid dir",2) end
  if dir>=5 then
    return dir
  end
  if dir ==4 then return 1 end
  return dir+1
end
function bound(dir,x,y,z,width,height,depth)
 if not names[dir] then error("invalid dir",2) end
 if not (x and y and z and width and height and depth) then error("must provide 7 args to bound",2) end
 if depth>0 then depth=depth-1 else depth=depth+1 end
 if height>0 then height=height-1 else height=height+1 end
 if width>0 then width=width-1 else width=width+1 end
 local x2,_,z2=addDir(dir,x,y,z,depth)
 local x3,_,z3=addDir(rotR(dir),x,y,z,width)
 if x2==x then
   x=x3
   z=z2
 else
   x=x2
   z=z3
 end
 return x,y+height,z
end