osgearth3.2生成云的代码，有调节云的颜色和厚度功能，有CreateCloud函数

osgEarth 3.2并没有内置生成云的函数，需要自行实现。以下是一个简单的示例代码，可以生成一个云层：

osg::Node* createCloud(osg::Vec3 center, float radius, osg::Vec4 color, float thickness)
{
    osg::Geode* geode = new osg::Geode();

    osg::Geometry* geometry = new osg::Geometry();
    geode->addDrawable(geometry);

    osg::Vec3Array* vertices = new osg::Vec3Array();
    vertices->push_back(osg::Vec3(center.x(), center.y(), center.z()));
    for (float angle = 0.0f; angle < osg::PI * 2.0f; angle += osg::PI / 8.0f)
    {
        float x = center.x() + radius * sin(angle);
        float y = center.y() + radius * cos(angle);
        vertices->push_back(osg::Vec3(x, y, center.z()));
    }
    geometry->setVertexArray(vertices);

    osg::Vec4Array* colors = new osg::Vec4Array();
    colors->push_back(color);
    geometry->setColorArray(colors, osg::Array::BIND_OVERALL);

    osg::DrawElementsUShort* primitive = new osg::DrawElementsUShort(osg::PrimitiveSet::TRIANGLE_FAN, 0);
    for (unsigned int i = 1; i < vertices->size(); ++i)
    {
        primitive->push_back(0);
        primitive->push_back(i);
        primitive->push_back(i == vertices->size() - 1 ? 1 : i + 1);
    }
    geometry->addPrimitiveSet(primitive);

    osgEarth::AltitudeSymbol* alt = geode->getOrCreateStateSet()->getOrCreateUniform<osgEarth::AltitudeSymbol>("oe_layer_altitude", osgEarth::AltitudeSymbol::create());
    alt->clamping() = osgEarth::AltitudeSymbol::CLAMP_TO_TERRAIN;
    alt->technique() = osgEarth::AltitudeSymbol::TECHNIQUE_DRAPE;

    osgEarth::ModelLayer* cloudLayer = new osgEarth::ModelLayer();
    cloudLayer->setName("Clouds");
    cloudLayer->setEnabled(true);
    cloudLayer->setMaxVisibleRange(2000, 100000);

    osgEarth::ModelSourceOptions cloudModelOptions;
    cloudModelOptions.color() = color;
    cloudModelOptions.alphaBlending() = true;
    cloudModelOptions.alphaBlending().setFunction(osg::StateAttribute::FUNCTION_ADD, osg::StateAttribute::FUNCTION_ADD);

    osg::MatrixTransform* transform = new osg::MatrixTransform();
    transform->addChild(geode);
    transform->setMatrix(osg::Matrix::scale(1.0f, 1.0f, thickness));
    cloudLayer->getModelSourceOptions() = cloudModelOptions;
    cloudLayer->addChild(transform);

    osgEarth::Registry::instance()->getMap()->addModelLayer(cloudLayer);

    return transform;
}

其中，`center`表示云层的中心点，`radius`表示云层的半径，`color`表示云层的颜色，`thickness`表示云层的厚度。可以根据实际需求调节这些参数以生成不同形状、颜色和厚度的云层。