39 lines
1.6 KiB
Lua
39 lines
1.6 KiB
Lua
function Point(x,y) return {x=x, y=y} end
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function Polygon(name, points)
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local function contains(self, p)
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local odd, eps = false, 1e-9
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local function rayseg(p, a, b)
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if a.y > b.y then a, b = b, a end
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if p.y == a.y or p.y == b.y then p.y = p.y + eps end
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if p.y < a.y or p.y > b.y or p.x > math.max(a.x, b.x) then return false end
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if p.x < math.min(a.x, b.x) then return true end
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local red = a.x == b.x and math.huge or (b.y-a.y)/(b.x-a.x)
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local blu = a.x == p.x and math.huge or (p.y-a.y)/(p.x-a.x)
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return blu >= red
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end
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for i, a in ipairs(self.points) do
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local b = self.points[i%#self.points+1]
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if rayseg(p, a, b) then odd = not odd end
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end
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return odd
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end
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return {name=name, points=points, contains=contains}
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end
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polygons = {
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Polygon("square", { Point(0,0), Point(10,0), Point(10,10), Point(0,10) }),
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Polygon("squarehole", { Point(0,0), Point(10,0), Point(10,10), Point(0,10), Point(2.5,2.5), Point(7.5,2.5), Point(7.5,7.5), Point(2.5,7.5) }),
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Polygon("strange", { Point(0,0), Point(2.5,2.5), Point(0, 10), Point(2.5,7.5), Point(7.5,7.5), Point(10,10), Point(10,0), Point(2.5,2.5) }),
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Polygon("hexagon", { Point(3,0), Point(7,0), Point(10,5), Point(7,10), Point(3,10), Point(0,5) })
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}
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points = { Point(5,5), Point(5,8), Point(-10,5), Point(0,5), Point(10,5), Point(8,5), Point(10,10) }
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for _,poly in ipairs(polygons) do
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print("Does '"..poly.name.."' contain the point..")
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for _,pt in ipairs(points) do
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print(string.format(" (%3.f, %2.f)? %s", pt.x, pt.y, tostring(poly:contains(pt))))
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end
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print()
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end
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