在 LÖVE 實作追蹤系統

前言

之前用 actionscript3.0 做守塔遊戲的時候，有做了一個簡單的追蹤系統，現在把它移植到 LÖVE 上。

追蹤系統可以用在導彈，或是其它需要尾隨的應用。

 

範例程式下載

Tracker.love

 

情境說明

建立四個半徑不同大小的圓，追蹤的速度與半徑大小成反比；最小的圓追滑鼠，剩下的分別追比自己小一階的圓。

 

Screenshot

 

程式碼(都在範例檔案內)

main.lua

require("lua/Circle")

require("lua/Tracker")

function love.load()

    mouse = {}

    circle1 = Circle.create(5)

    circle2 = Circle.create(10)

    circle3 = Circle.create(15)

    circle4 = Circle.create(20)

end

function love.update(dt)

    -- we need tracker/target provide x,y index for Tracker system

    -- let mouse provide x,y index

    mouse.x, mouse.y = love.mouse.getPosition()

    -- args = speed, tracker, target

    Tracker.trace(8, circle1, mouse)

    Tracker.trace(6, circle2, circle1)

    Tracker.trace(4, circle3, circle2)

    Tracker.trace(2, circle4, circle3)

end

function love.draw()

    circle1:draw()

    circle2:draw()

    circle3:draw()

    circle4:draw()

end

conf.lua

function love.conf(t)

    t.title = "Tracker"         -- The title of the window the game is in (string)

    t.author = "bmzz"           -- The author of the game (string)

    t.identity = nil            -- The name of the save directory (string)

    t.version = 072             -- The LOVE version this game was made for (number)

    t.console = false           -- Attach a console (boolean, Windows only)

    t.screen.width = 800        -- The window width (number)

    t.screen.height = 600       -- The window height (number)

    t.screen.fullscreen = false -- Enable fullscreen (boolean)

    t.screen.vsync = true       -- Enable vertical sync (boolean)

    t.screen.fsaa = 0           -- The number of FSAA-buffers (number)

    t.modules.joystick = false  -- Enable the joystick module (boolean)

    t.modules.audio = false     -- Enable the audio module (boolean)

    t.modules.keyboard = false  -- Enable the keyboard module (boolean)

    t.modules.event = true      -- Enable the event module (boolean)

    t.modules.image = false     -- Enable the image module (boolean)

    t.modules.graphics = true   -- Enable the graphics module (boolean)

    t.modules.timer = true      -- Enable the timer module (boolean)

    t.modules.mouse = true      -- Enable the mouse module (boolean)

    t.modules.sound = false     -- Enable the sound module (boolean)

    t.modules.physics = false   -- Enable the physics module (boolean)

end

lua/Circle.lua

Circle = {}

Circle.__index = Circle

function Circle.create(radius, attributes)

    attrs = attributes or {}

    local self = {}

    setmetatable(self, Circle)

    self.radius = radius

    self.segments = radius / 2

    if self.segments < 50 then self.segments = 50 end

    self.mode = attrs.mode or "line"

    self.x = attrs.x or 0

    self.y = attrs.y or 0

    self.color = attrs.color or {255, 255, 255}

    return self

end

function Circle:draw()

    love.graphics.setColor(self.color)

    love.graphics.circle(self.mode, self.x, self.y, self.radius, self.segments)

end

lua/Tracker.lua

Tracker = {}

function Tracker.trace(speed, tracker, target)

    local diffx = target.x - tracker.x

    local diffy = target.y - tracker.y

    local dist = math.sqrt(diffx ^ 2 + diffy ^ 2)

    local perc = speed / dist

    if dist > speed then

        tracker.x = tracker.x + diffx * perc

        tracker.y = tracker.y + diffy * perc

    else

        tracker.x = target.x

        tracker.y = target.y

    end

end