mirror of
https://github.com/kepler155c/opus
synced 2024-11-18 22:54:51 +00:00
89 lines
2.8 KiB
Lua
89 lines
2.8 KiB
Lua
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-- 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 ipairs = ipairs
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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 Heuristics = require (_PATH .. '.core.heuristics')
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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, finder, clearance, 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(finder, openList, node, neighbour, endNode, clearance, heuristic, overrideCostEval)
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local oldG = neighbour._g
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local cmpCost = overrideCostEval or computeCost
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cmpCost(node, neighbour, finder, clearance, heuristic)
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if neighbour._g < oldG then
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local nClearance = neighbour._clearance[finder._walkable]
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local pushThisNode = clearance and nClearance and (nClearance >= clearance)
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if (clearance and pushThisNode) or (not clearance) 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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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, clearance, toClear, overrideHeuristic, overrideCostEval)
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local heuristic = overrideHeuristic or finder._heuristic
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local openList = Heap()
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startNode._g = 0
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startNode._h = 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, finder._walkable, finder._allowDiagonal, finder._tunnel)
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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(finder, openList, node, neighbour, endNode, clearance, heuristic, overrideCostEval)
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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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