给定一个x,y点数组,如何按顺时针顺序(在它们的整体平均中心点附近)对该数组的点排序?我的目标是将这些点传递给线创建函数,以得到看起来很“实心”的东西,尽可能凸,没有线相交。
对于它的价值,我正在使用Lua,但任何伪代码都将不胜感激。
更新:作为参考,这是基于Ciamej出色答案的Lua代码(忽略我的“ app”前缀):
function appSortPointsClockwise(points)
local centerPoint = appGetCenterPointOfPoints(points)
app.pointsCenterPoint = centerPoint
table.sort(points, appGetIsLess)
return points
end
function appGetIsLess(a, b)
local center = app.pointsCenterPoint
if a.x >= 0 and b.x < 0 then return true
elseif a.x == 0 and b.x == 0 then return a.y > b.y
end
local det = (a.x - center.x) * (b.y - center.y) - (b.x - center.x) * (a.y - center.y)
if det < 0 then return true
elseif det > 0 then return false
end
local d1 = (a.x - center.x) * (a.x - center.x) + (a.y - center.y) * (a.y - center.y)
local d2 = (b.x - center.x) * (b.x - center.x) + (b.y - center.y) * (b.y - center.y)
return d1 > d2
end
function appGetCenterPointOfPoints(points)
local pointsSum = {x = 0, y = 0}
for i = 1, #points do pointsSum.x = pointsSum.x + points[i].x; pointsSum.y = pointsSum.y + points[i].y end
return {x = pointsSum.x / #points, y = pointsSum.y / #points}
end
ipairs(tbl)
,可将tbl 的索引和值从1 迭代到#tbl。因此,对于总和计算,您可以执行此操作,大多数人认为这看起来更干净:for _, p in ipairs(points) do pointsSum.x = pointsSum.x + p.x; pointsSum.y = pointsSum.y + p.y end
ipairs
比for循环的数字慢得多。