mirror of https://github.com/kepler155c/opus
98 lines
3.6 KiB
Lua
98 lines
3.6 KiB
Lua
--- Heuristic functions for search algorithms.
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-- A <a href="http://theory.stanford.edu/~amitp/GameProgramming/Heuristics.html">distance heuristic</a>
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-- provides an *estimate of the optimal distance cost* from a given location to a target.
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-- As such, it guides the pathfinder to the goal, helping it to decide which route is the best.
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--
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-- This script holds the definition of some built-in heuristics available through jumper.
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--
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-- Distance functions are internally used by the `pathfinder` to evaluate the optimal path
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-- from the start location to the goal. These functions share the same prototype:
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-- local function myHeuristic(nodeA, nodeB)
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-- -- function body
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-- end
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-- Jumper features some built-in distance heuristics, namely `MANHATTAN`, `EUCLIDIAN`, `DIAGONAL`, `CARDINTCARD`.
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-- You can also supply your own heuristic function, following the same template as above.
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local abs = math.abs
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local sqrt = math.sqrt
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local sqrt2 = sqrt(2)
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local max, min = math.max, math.min
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local Heuristics = {}
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--- Manhattan distance.
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-- <br/>This heuristic is the default one being used by the `pathfinder` object.
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-- <br/>Evaluates as <code>distance = |dx|+|dy|</code>
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-- @class function
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-- @tparam node nodeA a node
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-- @tparam node nodeB another node
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-- @treturn number the distance from __nodeA__ to __nodeB__
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-- @usage
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-- -- First method
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-- pathfinder:setHeuristic('MANHATTAN')
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-- -- Second method
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-- local Distance = require ('jumper.core.heuristics')
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-- pathfinder:setHeuristic(Distance.MANHATTAN)
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function Heuristics.MANHATTAN(nodeA, nodeB)
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local dx = abs(nodeA._x - nodeB._x)
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local dy = abs(nodeA._y - nodeB._y)
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local dz = abs(nodeA._z - nodeB._z)
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return (dx + dy + dz)
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end
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--- Euclidian distance.
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-- <br/>Evaluates as <code>distance = squareRoot(dx*dx+dy*dy)</code>
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-- @class function
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-- @tparam node nodeA a node
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-- @tparam node nodeB another node
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-- @treturn number the distance from __nodeA__ to __nodeB__
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-- @usage
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-- -- First method
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-- pathfinder:setHeuristic('EUCLIDIAN')
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-- -- Second method
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-- local Distance = require ('jumper.core.heuristics')
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-- pathfinder:setHeuristic(Distance.EUCLIDIAN)
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function Heuristics.EUCLIDIAN(nodeA, nodeB)
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local dx = nodeA._x - nodeB._x
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local dy = nodeA._y - nodeB._y
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local dz = nodeA._z - nodeB._z
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return sqrt(dx*dx+dy*dy+dz*dz)
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end
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--- Diagonal distance.
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-- <br/>Evaluates as <code>distance = max(|dx|, abs|dy|)</code>
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-- @class function
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-- @tparam node nodeA a node
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-- @tparam node nodeB another node
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-- @treturn number the distance from __nodeA__ to __nodeB__
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-- @usage
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-- -- First method
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-- pathfinder:setHeuristic('DIAGONAL')
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-- -- Second method
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-- local Distance = require ('jumper.core.heuristics')
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-- pathfinder:setHeuristic(Distance.DIAGONAL)
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function Heuristics.DIAGONAL(nodeA, nodeB)
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local dx = abs(nodeA._x - nodeB._x)
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local dy = abs(nodeA._y - nodeB._y)
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return max(dx,dy)
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end
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--- Cardinal/Intercardinal distance.
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-- <br/>Evaluates as <code>distance = min(dx, dy)*squareRoot(2) + max(dx, dy) - min(dx, dy)</code>
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-- @class function
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-- @tparam node nodeA a node
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-- @tparam node nodeB another node
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-- @treturn number the distance from __nodeA__ to __nodeB__
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-- @usage
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-- -- First method
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-- pathfinder:setHeuristic('CARDINTCARD')
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-- -- Second method
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-- local Distance = require ('jumper.core.heuristics')
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-- pathfinder:setHeuristic(Distance.CARDINTCARD)
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function Heuristics.CARDINTCARD(nodeA, nodeB)
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local dx = abs(nodeA._x - nodeB._x)
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local dy = abs(nodeA._y - nodeB._y)
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return min(dx,dy) * sqrt2 + max(dx,dy) - min(dx,dy)
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end
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return Heuristics |