圆周环绕：切向加向心的力学舞

fx-hplink

local OrbitMotion = {}
local CONST = { KEY = "OrbitMotion", TANGENT = 120, CENTRIPETAL = 200 }

function OrbitMotion.Cast(myID, targetID)
    OrbitMotion._sched = SL:Schedule(function(dt)
        OrbitMotion:Update(dt, targetID)
    end, 0.02)
end

function OrbitMotion:Update(dt, targetID)
    local mx = SL:GetValue("ACTOR_POSITION_X", targetID)
    local my = SL:GetValue("ACTOR_POSITION_Y", targetID)
    local ox = SL:GetValue("ACTOR_POSITION_X", self._myID)
    local oy = SL:GetValue("ACTOR_POSITION_Y", self._myID)
    local dx, dy = mx - ox, my - oy
    local d = math.sqrt(dx * dx + dy * dy)
    if d < 1 then return end
    local tangentX = -dy / d * CONST.TANGENT
    local tangentY = dx / d * CONST.TANGENT
    local centripetalX = -dx / d * CONST.CENTRIPETAL
    local centripetalY = -dy / d * CONST.CENTRIPETAL
    SL:SetActorVelocity(targetID, tangentX + centripetalX, tangentY + centripetalY)
end

return OrbitMotion