Lua矩形重叠：反向分离的相交判定

local function isApart(a, b)
    return a.x2 < b.x1 or b.x2 < a.x1
        or a.y2 < b.y1 or b.y2 < a.y1
end

local function overlapArea(a, b)
    if isApart(a, b) then return 0 end
    local w = math.min(a.x2, b.x2)
        - math.max(a.x1, b.x1)
    local h = math.min(a.y2, b.y2)
        - math.max(a.y1, b.y1)
    return w * h
end
local p = getplayerbyname("rect01")
local a = {x1 = 0, y1 = 0, x2 = 4, y2 = 4}
local b = {x1 = 2, y1 = 2, x2 = 6, y2 = 6}
sendmsg(p, 1, "重叠面积 " .. overlapArea(a, b))