Qt Quick Particles Examples - CustomParticle | Qt Quick 5.9

Qt 5.9 | Qt Quick | Qt Quick Particles Examples - CustomParticle

Qt 5.9.4 Reference Documentation

# Qt Quick Particles Examples - CustomParticle

This is a collection of small QML examples relating to using CustomParticle in the particle system. Each example is a small QML file emphasizing a different way to use CustomParticle.

Blur Particles adds a blur effect to the particles, which increases over the particle's life time. It uses a custom vertex shader:

      vertexShader:"
          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);
          }
      "

to propagate life time simulation to a custom fragment shader:

      fragmentShader: "
          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;
          }"

which has access to both the normal image sampler and a blurred sampler, the image plus a ShaderEffect.

Fragment Shader just uses the particle system as a vertex delivery system.

      fragmentShader: "
          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;
          }"

Image Colors uses CustomParticle to assign colors to particles based on their location in a picture. The vertex shader,

      vertexShader:"
          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();
          }
      "

passes along the starting position for each vertex to the fragment shader,

      fragmentShader: "
          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;
      }"

which uses it to determine the color for that particle.

Files:

- particles/customparticle/customparticle.qml
- particles/customparticle/content/blurparticles.qml
- particles/customparticle/content/fragmentshader.qml
- particles/customparticle/content/imagecolors.qml
- particles/customparticle/main.cpp
- particles/customparticle/customparticle.pro
- particles/customparticle/customparticle.qmlproject
- particles/customparticle/customparticle.qrc