mirror of
https://github.com/kepler155c/opus
synced 2024-11-15 13:14:49 +00:00
78 lines
2.2 KiB
Lua
78 lines
2.2 KiB
Lua
-- Astar algorithm
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-- This actual implementation of A-star is based on
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-- [Nash A. & al. pseudocode](http://aigamedev.com/open/tutorials/theta-star-any-angle-paths/)
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if (...) then
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-- Internalization
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local huge = math.huge
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-- Dependancies
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local _PATH = (...):match('(.+)%.search.astar$')
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local Heap = require (_PATH.. '.core.bheap')
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-- 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)
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if node._g + mCost < neighbour._g then
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neighbour._parent = node
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neighbour._g = node._g + mCost
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neighbour.heading = heading
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end
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end
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-- 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
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neighbour._h = heuristic(endNode, neighbour)
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neighbour._f = neighbour._g + neighbour._h
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openList:push(neighbour)
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neighbour._opened = true
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end
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end
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-- Calculates a path.
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-- 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()
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startNode._g = 0
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startNode._h = finder._heuristic(endNode, startNode)
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startNode._f = startNode._g + startNode._h
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openList:push(startNode)
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toClear[startNode] = true
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startNode._opened = true
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while not openList:empty() do
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local node = openList:pop()
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node._closed = true
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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
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local neighbour = neighbours[i]
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if not neighbour._closed then
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toClear[neighbour] = true
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if not neighbour._opened then
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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)
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end
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end
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--[[
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printf('x:%d y:%d z:%d g:%d', node.x, node.y, node.z, node._g)
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for i = 1,#neighbours do
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local n = neighbours[i]
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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)
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end
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--]]
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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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