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  254. <h1 class="page">Main Update Loop</h1>
  255. <div id="preamble">
  256. <div class="sectionbody">
  257. <div class="paragraph">
  258. <p>Extending your application from com.jme3.app.<a href="../intermediate/simpleapplication.html" class="page">SimpleApplication</a> provides you with an update loop. This is where you implement your game logic (game mechanics).</p>
  259. </div>
  260. <div class="paragraph">
  261. <p>Some usage examples: Here you remote-control NPCs (computer controlled characters), generate game events, and respond to user input.</p>
  262. </div>
  263. <div class="paragraph">
  264. <p>To let you see the main update loop in context, understand that the SimpleApplication does the following:</p>
  265. </div>
  266. <div class="ulist">
  267. <ul>
  268. <li>
  269. <p><strong>Initialization</strong> – Execute <code>simpleInitApp()</code> method once.</p>
  270. </li>
  271. <li>
  272. <p><strong>Main Update Loop</strong></p>
  273. <div class="olist loweralpha">
  274. <ol class="loweralpha" type="a">
  275. <li>
  276. <p>Input listeners respond to mouse clicks and keyboard presses – <a href="input_handling.html" class="page">Input handling</a></p>
  277. </li>
  278. <li>
  279. <p>Update game state:</p>
  280. <div class="olist lowerroman">
  281. <ol class="lowerroman" type="i">
  282. <li>
  283. <p>Update overall game state – Execute <a href="application_states.html" class="page">Application States</a></p>
  284. </li>
  285. <li>
  286. <p>User code update – Execute <code>simpleUpdate()</code> method</p>
  287. </li>
  288. <li>
  289. <p>Logical update of entities – Execute <a href="custom_controls.html" class="page">Custom Controls</a></p>
  290. </li>
  291. </ol>
  292. </div>
  293. </li>
  294. <li>
  295. <p>Render audio and video</p>
  296. <div class="olist lowerroman">
  297. <ol class="lowerroman" type="i">
  298. <li>
  299. <p><a href="application_states.html" class="page">Application States</a> rendering.</p>
  300. </li>
  301. <li>
  302. <p>Scene rendering.</p>
  303. </li>
  304. <li>
  305. <p>User code rendering – Execute <code>simpleRender()</code> method.</p>
  306. </li>
  307. </ol>
  308. </div>
  309. </li>
  310. <li>
  311. <p>Repeat loop.</p>
  312. </li>
  313. </ol>
  314. </div>
  315. </li>
  316. <li>
  317. <p><strong>Quit</strong> – If user requests <code>exit()</code>, execute <code>cleanup()</code> and <code>destroy()</code>.<br>
  318. The jME window closes and the loop ends.</p>
  319. </li>
  320. </ul>
  321. </div>
  322. </div>
  323. </div>
  324. <div class="sect1">
  325. <h2 id="usage"><a class="anchor" href="#usage"></a>Usage</h2>
  326. <div class="sectionbody">
  327. <div class="paragraph">
  328. <p>In a trivial <a href="../intermediate/simpleapplication.html" class="page">SimpleApplication</a> (such as a <a href="../beginner.html" class="page">Hello World tutorial</a>), all code is either in the <code>simpleInitApp()</code> (initialization) or <code>simpleUpdate()</code> (behaviour) method – or in a helper method/class that is called from one of these two. This trivial approach will make your main class very long, hard to read, and hard to maintain. You don&#8217;t need to load the whole scene at once, and you don&#8217;t need to run all conditionals tests all the time.</p>
  329. </div>
  330. <div class="paragraph">
  331. <p>It&#8217;s a best practice to modularize your game mechanics and spread out initialization and update loop code over several Java objects:</p>
  332. </div>
  333. <div class="ulist">
  334. <ul>
  335. <li>
  336. <p>Move modular code blocks from the <code>simpleInitApp()</code> method into <a href="application_states.html" class="page">AppStates</a>. Attach AppStates to initialize custom subsets of “one dungeon, and detach it when the player exits this “dungeon.<br>
  337. Examples: Weather/sky audio and visuals, physics collision shapes, sub-rootnodes of individual dungeons including dungeon NPCs, etc.</p>
  338. </li>
  339. <li>
  340. <p>Move modular code blocks from the <code>simpleUpdate()</code> method into the update loops of <a href="custom_controls.html" class="page">Custom Controls</a> to control individual entity behavior (NPCs), and into the update method of <a href="application_states.html" class="page">AppStates</a> to control world events.<br>
  341. Examples: Weather behaviour, light behaviour, physics behaviour, individual NPC behaviour, trap behaviour, etc.</p>
  342. </li>
  343. </ul>
  344. </div>
  345. </div>
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