ComputerCraft turtle code for building a sphere of material.

buildSphere.lua

-- v. 1.0 : Based off of v. 1.1 of Circle Platform.  Again, a bit messy, dealing
-- with going over the entire area of r^3 cube (and plus the distance for it to 
-- get back to the center), but this should do the trick.

-- The MIT License (MIT)

-- Copyright (c) 2012 Alexander Williams

-- Permission is hereby granted, free of charge, to any person obtaining a copy
-- of this software and associated documentation files (the "Software"), to deal
-- in the Software without restriction, including without limitation the rights
-- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-- copies of the Software, and to permit persons to whom the Software is
-- furnished to do so, subject to the following conditions:

-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.

-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-- SOFTWARE.

local tArgs = {...}
local radius = tonumber(tArgs[1])
local slot = 1
local turnflag = true

turtle.select(slot)

for k = -radius,radius do
    
    turnflag = true
    
    for i = 1,radius do
        turtle.back()
    end
    
    turtle.turnRight()
    for i = 1,radius do
        turtle.back()
    end
    turtle.turnLeft()
    
    for i = -radius, radius do
      for j = -radius, radius do
          
        if turtle.getItemCount(slot) == 0 then
          slot = slot + 1
          if slot == 17 then 
              slot = 1 -- Let's hope something will be there.
              if turtle.getItemCount(slot) == 0 then
                return
              end
          end
          turtle.select(slot)
        end
    
        if math.sqrt(i*i + j*j + k*k) <= radius then
            turtle.placeDown()
        end
        
          turtle.forward()
      
      end
       
        if turnflag == true then
          turtle.turnRight()
          turtle.forward()
          turtle.turnRight()
          turtle.forward()
          turnflag = false
        else
          turtle.turnLeft()
          turtle.forward()
          turtle.turnLeft()
          turtle.forward()
    
          turnflag = true
        end
      
    end
    
    -- now to return to the center of the platform
    for i=1,radius do
      turtle.forward()
    end
    
    turtle.turnLeft()
    
    for i=0,radius do
      turtle.back()
    end
    
    
    
    turtle.up()
end