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opus/sys/apis/jumper/search/astar.lua

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-- Astar algorithm
-- This actual implementation of A-star is based on
-- [Nash A. & al. pseudocode](http://aigamedev.com/open/tutorials/theta-star-any-angle-paths/)
if (...) then
-- Internalization
local huge = math.huge
-- Dependancies
local _PATH = (...):match('(.+)%.search.astar$')
local Heap = require (_PATH.. '.core.bheap')
-- Updates G-cost
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local function computeCost(node, neighbour, heuristic)
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local mCost, heading = heuristic(neighbour, node) -- Heuristics.EUCLIDIAN(neighbour, node)
if node._g + mCost < neighbour._g then
neighbour._parent = node
neighbour._g = node._g + mCost
neighbour._heading = heading
end
end
-- Updates vertex node-neighbour
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local function updateVertex(openList, node, neighbour, endNode, heuristic)
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local oldG = neighbour._g
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computeCost(node, neighbour, heuristic)
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if neighbour._g < oldG then
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if neighbour._opened then neighbour._opened = false end
neighbour._h = heuristic(endNode, neighbour)
neighbour._f = neighbour._g + neighbour._h
openList:push(neighbour)
neighbour._opened = true
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end
end
-- Calculates a path.
-- Returns the path from location `<startX, startY>` to location `<endX, endY>`.
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return function (finder, startNode, endNode, toClear)
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local openList = Heap()
startNode._g = 0
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startNode._h = finder._heuristic(endNode, startNode)
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startNode._f = startNode._g + startNode._h
openList:push(startNode)
toClear[startNode] = true
startNode._opened = true
while not openList:empty() do
local node = openList:pop()
node._closed = true
if node == endNode then return node end
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local neighbours = finder._grid:getNeighbours(node)
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for i = 1,#neighbours do
local neighbour = neighbours[i]
if not neighbour._closed then
toClear[neighbour] = true
if not neighbour._opened then
neighbour._g = huge
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neighbour._parent = nil
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end
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updateVertex(openList, node, neighbour, endNode, finder._heuristic)
end
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end
--[[
printf('x:%d y:%d z:%d g:%d', node._x, node._y, node._z, node._g)
for i = 1,#neighbours do
local n = neighbours[i]
printf('x:%d y:%d z:%d f:%f g:%f h:%d', n._x, n._y, n._z, n._f, n._g, n._heading or -1)
end
--]]
end
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return nil
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end
end