冰面打滑：刹不住的那一脚

fx-ice

function gameActor:UpdateMove(dt)
    local onIce = scene:IsOnIce(self._x, self._y)

    if not onIce then
        -- 受控模型: 目标直接给速度
        if self._moveTarget then
            local dx, dy = self:_ToTarget()
            self._vx, self._vy = dx * self._walkSpeed, dy * self._walkSpeed
        else
            self._vx = self._vx * 0.7; self._vy = self._vy * 0.7   -- 带出的速度快速衰减
        end
    else
        -- 惯性模型: 目标只给加速度, 低摩擦
        if self._moveTarget then
            local dx, dy = self:_ToTargetDir()
            self._vx = self._vx + dx * 300 * dt
            self._vy = self._vy + dy * 300 * dt
        end
        self._vx = self._vx * (1 - self._friction * 0.35 * dt)
        self._vy = self._vy * (1 - self._friction * 0.35 * dt)
        self:_ClampSpeed(260)                       -- 上限防无限加速
    end

    self._x = self._x + self._vx * dt
    self._y = self._y + self._vy * dt
end