Qt Quick Particles 示例 - 发射器

这是一组关于在 QML 粒子系统中使用发射器的示例。

弯曲的粒子形成了一个花朵状的图案，其中有六条旋转的辐条

这是一组与粒子系统中使用发射器相关的小型 QML 示例。每个示例都是一个小型 QML 文件，重点展示特定类型或功能。

通过“运动”生成的速度效果，主要通过移动发射器来实现强烈的粒子运动：

Emitter {
    id: trailsNormal
    system: sys1

    emitRate: 500
    lifeSpan: 2000

    y: mouseArea.pressed ? mouseArea.mouseY : circle.cy
    x: mouseArea.pressed ? mouseArea.mouseX : circle.cx

    velocity: PointDirection {xVariation: 4; yVariation: 4;}
    acceleration: PointDirection {xVariation: 10; yVariation: 10;}
    velocityFromMovement: 8

    size: 8
    sizeVariation: 4
}

“Burst”和“pulse”分别调用两个相同发射器的 burst 和 pulse 方法。

    if (root.lastWasPulse) {
        burstEmitter.burst(500);
        root.lastWasPulse = false;
    } else {
        pulseEmitter.pulse(500);
        root.lastWasPulse = true;
    }

请注意，“burst”方法接受要发射的粒子数量作为参数，而“pulse”方法接受发射持续时间（以毫秒为单位）作为参数。这会产生略有不同的行为，在该示例中很容易观察到。

“自定义发射器”通过连接到 emitParticles 信号，在粒子发射时对其数据设置任意值；

onEmitParticles: (particles) => {
    for (var i=0; i<particles.length; i++) {
        let particle = particles[i];
        particle.startSize = Math.max(02,Math.min(492,Math.tan(particle.t/2)*24));
        let theta = Math.floor(Math.random() * 6.0);
        particle.red = theta == 0 || theta == 1 || theta == 2 ? 0.2 : 1;
        particle.green = theta == 2 || theta == 3 || theta == 4 ? 0.2 : 1;
        particle.blue = theta == 4 || theta == 5 || theta == 0 ? 0.2 : 1;
        theta /= 6.0;
        theta *= 2.0*Math.PI;
        theta += sys.convert(sys.petalRotation);//Convert from degrees to radians
        particle.initialVX = sys.petalLength * Math.cos(theta);
        particle.initialVY = sys.petalLength * Math.sin(theta);
        particle.initialAX = particle.initialVX * -0.5;
        particle.initialAY = particle.initialVY * -0.5;
    }
}

此功能用于发射沿六个旋转辐条轨迹运动的曲线粒子。

“发射遮罩”可在发射器上设置图像遮罩，以任意形状发射粒子。

shape: MaskShape {
    source: "images/starfish_mask.png"
}

“最大发射量”功能可确保每次发射的粒子数量不超过特定数值。通过本示例，可以直观地观察到达到限制时会发生什么情况。

“形状与方向”功能利用TargetDirection

shape: EllipseShape {fill: false}
velocity: TargetDirection {
    targetX: root.width/2
    targetY: root.height/2
    proportionalMagnitude: true
    magnitude: 0.5
}

这会使粒子以比例速度朝椭圆中心移动，并在移动过程中保持椭圆轮廓。

TrailEmitter 使用该类型在场景中为火焰粒子添加尾随的烟雾粒子。

onEmitParticles: (particles) => {
    for (var i=0; i<particles.length; i++) {
        let particle = particles[i];
        particle.startSize = Math.max(02,Math.min(492,Math.tan(particle.t/2)*24));
        let theta = Math.floor(Math.random() * 6.0);
        particle.red = theta == 0 || theta == 1 || theta == 2 ? 0.2 : 1;
        particle.green = theta == 2 || theta == 3 || theta == 4 ? 0.2 : 1;
        particle.blue = theta == 4 || theta == 5 || theta == 0 ? 0.2 : 1;
        theta /= 6.0;
        theta *= 2.0*Math.PI;
        theta += sys.convert(sys.petalRotation);//Convert from degrees to radians
        particle.initialVX = sys.petalLength * Math.cos(theta);
        particle.initialVY = sys.petalLength * Math.sin(theta);
        particle.initialAX = particle.initialVX * -0.5;
        particle.initialAY = particle.initialVY * -0.5;
    }
}

示例项目 @ code.qt.io

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