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<?xml version="1.0" encoding="UTF-8"?>
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<td >Qt 5.9</td><td ><a href="qtquick-index.html">Qt Quick</a></td><td >Qt Quick Particles Examples - CustomParticle</td></tr></table><table class="buildversion"><tr>
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<h1 class="title">Qt Quick Particles Examples - CustomParticle</h1>
<span class="subtitle"></span>
<!-- $$$particles/customparticle-description -->
<div class="descr"> <a name="details"></a>
<p class="centerAlign"><img src="images/qml-customparticle-example.png" alt="" /></p><p>This is a collection of small QML examples relating to using <a href="qml-qtquick-particles-customparticle.html">CustomParticle</a> in the particle system. Each example is a small QML file emphasizing a different way to use <a href="qml-qtquick-particles-customparticle.html">CustomParticle</a>.</p>
<p>Blur Particles adds a blur effect to the particles, which increases over the particle's life time. It uses a custom vertex shader:</p>
<pre class="qml">

  <span class="name">vertexShader</span>:<span class="string">&quot;
      uniform lowp float qt_Opacity;
      varying lowp float fFade;
      varying lowp float fBlur;

      void main() {
          defaultMain();
          highp float t = (qt_Timestamp - qt_ParticleData.x) / qt_ParticleData.y;
          highp float fadeIn = min(t * 10., 1.);
          highp float fadeOut = 1. - max(0., min((t - 0.75) * 4., 1.));

          fFade = fadeIn * fadeOut * qt_Opacity;
          fBlur = max(0.2 * t, t * qt_ParticleR);
      }
  &quot;</span>

</pre>
<p>to propagate life time simulation to a custom fragment shader:</p>
<pre class="qml">

  <span class="name">fragmentShader</span>: <span class="string">&quot;
      uniform sampler2D source;
      uniform sampler2D blurred;
      varying highp vec2 qt_TexCoord0;
      varying highp float fBlur;
      varying highp float fFade;
      void main() {
          gl_FragColor = mix(texture2D(source, qt_TexCoord0), texture2D(blurred, qt_TexCoord0), min(1.0,fBlur*3.0)) * fFade;
      }&quot;</span>

</pre>
<p>which has access to both the normal image sampler and a blurred sampler, the image plus a <a href="qml-qtquick-shadereffect.html">ShaderEffect</a>.</p>
<p>Fragment Shader just uses the particle system as a vertex delivery system.</p>
<pre class="qml">

  <span class="name">fragmentShader</span>: <span class="string">&quot;
      varying highp vec2 fPos;
      varying lowp float fFade;
      varying highp vec2 qt_TexCoord0;
      void main() {//*2 because this generates dark colors mostly
          highp vec2 circlePos = qt_TexCoord0*2.0 - vec2(1.0,1.0);
          highp float dist = length(circlePos);
          highp float circleFactor = max(min(1.0 - dist, 1.0), 0.0);
          gl_FragColor = vec4(fPos.x*2.0 - fPos.y, fPos.y*2.0 - fPos.x, fPos.x*fPos.y*2.0, 0.0) * circleFactor * fFade;
      }&quot;</span>

</pre>
<p>Image Colors uses <a href="qml-qtquick-particles-customparticle.html">CustomParticle</a> to assign colors to particles based on their location in a picture. The vertex shader,</p>
<pre class="qml">

  <span class="name">vertexShader</span>:<span class="string">&quot;
      uniform highp float maxWidth;
      uniform highp float maxHeight;
      varying highp vec2 fTex2;
      varying lowp float fFade;
      uniform lowp float qt_Opacity;

      void main() {

          fTex2 = vec2(qt_ParticlePos.x, qt_ParticlePos.y);
          //Uncomment this next line for each particle to use full texture, instead of the solid color at the center of the particle.
          //fTex2 = fTex2 + ((- qt_ParticleData.z / 2. + qt_ParticleData.z) * qt_ParticleTex); //Adjusts size so it's like a chunk of image.
          fTex2 = fTex2 / vec2(maxWidth, maxHeight);
          highp float t = (qt_Timestamp - qt_ParticleData.x) / qt_ParticleData.y;
          fFade = min(t*4., (1.-t*t)*.75) * qt_Opacity;
          defaultMain();
      }
  &quot;</span>

</pre>
<p>passes along the starting position for each vertex to the fragment shader,</p>
<pre class="qml">

  <span class="name">fragmentShader</span>: <span class="string">&quot;
      uniform sampler2D particleTexture;
      uniform sampler2D pictureTexture;
      varying highp vec2 qt_TexCoord0;
      varying highp vec2 fTex2;
      varying lowp float fFade;
      void main() {
          gl_FragColor = texture2D(pictureTexture, fTex2) * texture2D(particleTexture, qt_TexCoord0).w * fFade;
  }&quot;</span>

</pre>
<p>which uses it to determine the color for that particle.</p>
<p>Files:</p>
<ul>
<li><a href="qtquick-particles-customparticle-customparticle-qml.html">particles/customparticle/customparticle.qml</a></li>
<li><a href="qtquick-particles-customparticle-content-blurparticles-qml.html">particles/customparticle/content/blurparticles.qml</a></li>
<li><a href="qtquick-particles-customparticle-content-fragmentshader-qml.html">particles/customparticle/content/fragmentshader.qml</a></li>
<li><a href="qtquick-particles-customparticle-content-imagecolors-qml.html">particles/customparticle/content/imagecolors.qml</a></li>
<li><a href="qtquick-particles-customparticle-main-cpp.html">particles/customparticle/main.cpp</a></li>
<li><a href="qtquick-particles-customparticle-customparticle-pro.html">particles/customparticle/customparticle.pro</a></li>
<li><a href="qtquick-particles-customparticle-customparticle-qmlproject.html">particles/customparticle/customparticle.qmlproject</a></li>
<li><a href="qtquick-particles-customparticle-customparticle-qrc.html">particles/customparticle/customparticle.qrc</a></li>
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