166 lines
5.2 KiB
Lua
166 lines
5.2 KiB
Lua
local expect = dofile("rom/modules/main/cc/expect.lua").expect
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CHANNEL_GPS = 65534
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local function trilaterate( A, B, C )
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local a2b = B.vPosition - A.vPosition
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local a2c = C.vPosition - A.vPosition
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if math.abs( a2b:normalize():dot( a2c:normalize() ) ) > 0.999 then
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return nil
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end
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local d = a2b:length()
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local ex = a2b:normalize( )
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local i = ex:dot( a2c )
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local ey = (a2c - ex * i):normalize()
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local j = ey:dot( a2c )
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local ez = ex:cross( ey )
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local r1 = A.nDistance
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local r2 = B.nDistance
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local r3 = C.nDistance
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local x = (r1 * r1 - r2 * r2 + d * d) / (2 * d)
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local y = (r1 * r1 - r3 * r3 - x * x + (x - i) * (x - i) + j * j) / (2 * j)
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local result = A.vPosition + ex * x + ey * y
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local zSquared = r1 * r1 - x * x - y * y
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if zSquared > 0 then
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local z = math.sqrt( zSquared )
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local result1 = result + ez * z
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local result2 = result - ez * z
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local rounded1, rounded2 = result1:round( 0.01 ), result2:round( 0.01 )
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if rounded1.x ~= rounded2.x or rounded1.y ~= rounded2.y or rounded1.z ~= rounded2.z then
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return rounded1, rounded2
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else
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return rounded1
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end
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end
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return result:round( 0.01 )
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end
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local function narrow( p1, p2, fix )
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local dist1 = math.abs( (p1 - fix.vPosition):length() - fix.nDistance )
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local dist2 = math.abs( (p2 - fix.vPosition):length() - fix.nDistance )
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if math.abs(dist1 - dist2) < 0.01 then
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return p1, p2
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elseif dist1 < dist2 then
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return p1:round( 0.01 )
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else
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return p2:round( 0.01 )
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end
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end
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function locate( _nTimeout, _bDebug )
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expect(1, _nTimeout, "number", "nil")
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expect(2, _bDebug, "boolean", "nil")
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-- Let command computers use their magic fourth-wall-breaking special abilities
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if commands then
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return commands.getBlockPosition()
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end
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-- Find a modem
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local sModemSide = nil
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for _, sSide in ipairs( rs.getSides() ) do
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if peripheral.getType( sSide ) == "modem" and peripheral.call( sSide, "isWireless" ) then
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sModemSide = sSide
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break
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end
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end
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if sModemSide == nil then
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if _bDebug then
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print( "No wireless modem attached" )
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end
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return nil
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end
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if _bDebug then
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print( "Finding position..." )
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end
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-- Open a channel
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local modem = peripheral.wrap( sModemSide )
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local bCloseChannel = false
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if not modem.isOpen( os.getComputerID() ) then
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modem.open( os.getComputerID() )
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bCloseChannel = true
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end
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-- Send a ping to listening GPS hosts
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modem.transmit( CHANNEL_GPS, os.getComputerID(), "PING" )
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-- Wait for the responses
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local tFixes = {}
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local pos1, pos2 = nil, nil
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local timeout = os.startTimer( _nTimeout or 2 )
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while true do
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local e, p1, p2, p3, p4, p5 = os.pullEvent()
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if e == "modem_message" then
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-- We received a reply from a modem
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local sSide, sChannel, sReplyChannel, tMessage, nDistance = p1, p2, p3, p4, p5
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if sSide == sModemSide and sChannel == os.getComputerID() and sReplyChannel == CHANNEL_GPS and nDistance then
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-- Received the correct message from the correct modem: use it to determine position
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if type(tMessage) == "table" and #tMessage == 3 and tonumber(tMessage[1]) and tonumber(tMessage[2]) and tonumber(tMessage[3]) then
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local tFix = { vPosition = vector.new( tMessage[1], tMessage[2], tMessage[3] ), nDistance = nDistance }
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if _bDebug then
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print( tFix.nDistance .. " metres from " .. tostring( tFix.vPosition ) )
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end
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if tFix.nDistance == 0 then
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pos1, pos2 = tFix.vPosition, nil
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else
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table.insert( tFixes, tFix )
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if #tFixes >= 3 then
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if not pos1 then
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pos1, pos2 = trilaterate( tFixes[1], tFixes[2], tFixes[#tFixes] )
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else
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pos1, pos2 = narrow( pos1, pos2, tFixes[#tFixes] )
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end
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end
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end
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if pos1 and not pos2 then
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break
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end
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end
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end
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elseif e == "timer" then
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-- We received a timeout
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local timer = p1
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if timer == timeout then
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break
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end
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end
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end
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-- Close the channel, if we opened one
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if bCloseChannel then
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modem.close( os.getComputerID() )
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end
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-- Return the response
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if pos1 and pos2 then
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if _bDebug then
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print( "Ambiguous position" )
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print( "Could be " .. pos1.x .. "," .. pos1.y .. "," .. pos1.z .. " or " .. pos2.x .. "," .. pos2.y .. "," .. pos2.z )
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end
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return nil
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elseif pos1 then
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if _bDebug then
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print( "Position is " .. pos1.x .. "," .. pos1.y .. "," .. pos1.z )
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end
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return pos1.x, pos1.y, pos1.z
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else
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if _bDebug then
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print( "Could not determine position" )
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end
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return nil
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end
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end
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