samples.libcna.com/PrimitivesSample.html at main · libcna/samples.libcna.com · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Primitives — CNA Samples</title>
<meta name="description" content="The XNA Primitives sample ported to C++ with CNA: drawing points, lines and triangles through a Begin/End batch.">
<link rel="stylesheet" href="assets/site.css">
</head>
<body>

<header class="site-head">
  <div class="wrap">
    <h1 class="site-title"><a href="index.html">CNA Samples</a></h1>
  </div>
</header>

<main class="wrap">

  <div class="detail-head">
    <h1>Primitives</h1>
  </div>
  <p class="origin">Ported from Microsoft's XNA 4.0 <em>Primitives Sample</em>.</p>
  <p class="sample-source">
    <a href="https://github.com/libcna/cna-samples/tree/develop/samples/PrimitivesSample">Source for this sample on GitHub ↗</a>
  </p>

  <img class="shot" src="assets/img/primitives.png" width="853" height="480"
       alt="A starfield with two Spacewar ships and a sun, drawn entirely from points and lines.">

  <a class="play" href="PrimitivesSample/PrimitivesSample_cna_samples.html" target="_blank" rel="noopener">Play ▸</a>
  <p class="play-note">Opens in a new tab and runs in this browser. Click the canvas first so it receives the keyboard.</p>

  <nav class="pager pager-before-about" aria-label="Sample navigation">
    <span></span>
    <a class="next" href="Primitives3D.html"><span class="label">Next</span>Primitives 3D</a>
  </nav>

  <section>
    <h2>About this sample</h2>
    <p>
      Spacewar's retro mode draws everything with points and lines. This sample takes the idea further and
      builds <code>PrimitiveBatch</code>, a small layer over <code>GraphicsDevice.DrawUserPrimitives</code>
      that lets you draw points, lines and triangles without setting up a vertex buffer for each shape.
    </p>
    <p>
      It follows the same Begin/End pattern as <code>SpriteBatch</code>: call <code>Begin</code>, call
      <code>AddVertex</code> as many times as you need, then <code>End</code>. Internally the batch fills an
      array of vertices and flushes it to the graphics device whenever the array runs out of room, so the
      number of draw calls stays low however many shapes you add.
    </p>
    <p>
      That makes it useful for more than drawing a game. Arbitrary primitives on demand are exactly what you
      want when visualising collision volumes, spatial partitions or any other piece of state that is easier
      to see than to read.
    </p>
    <p>The sample itself draws a scene from Spacewar to show the batch in use.</p>
  </section>

  <section>
    <h2>Controls</h2>
    <p>The sample runs on its own; the only control is how to leave it.</p>
    <table class="controls">
      <tr><th>Action</th><th>Keyboard</th><th>Gamepad</th></tr>
      <tr><td>Exit</td><td><kbd>Esc</kbd></td><td><kbd>Back</kbd></td></tr>
    </table>
    <p class="play-note">
      In the browser, exiting ends the sample rather than closing the tab — close the tab yourself when
      you are done.
    </p>
  </section>

  <nav class="pager">
    <span></span>
    <a class="next" href="Primitives3D.html"><span class="label">Next</span>Primitives 3D</a>
  </nav>

</main>

<footer class="site-foot">
  <div class="wrap">
    <p>
      The sample is Microsoft's, published under the Microsoft Permissive License.
      The C++ port and the WebAssembly build are CNA.
    </p>
  </div>
</footer>

</body>
</html>