fbx rendered grey problem

[ggslayer]

Hi, I'm new user for osg and opengl render, I occured a problem when learning osg, need some help.

I build osg with fbx plugin succeed, and load a fbx file from www.mixamo.com, model rendered succed, but render result is so grey, after some test, I can't resolve the grey problem,

The render result screenshot image: https://github.com/ggslayer/codebase/blob/master/2023-10-16%2018-38-58%20%E7%9A%84%E5%B1%8F%E5%B9%95%E6%88%AA%E5%9B%BE.png?raw=true

The fbx file downloaded from mixamo link: https://github.com/ggslayer/codebase/releases/download/fbx/dance.fbx

my code like this:

I can see the color in the view, but very grey, so I think the textures in fbx is loaded and render succeed,
I run the model in osgViewer, grey too.. but in some online 3d viewer and mixamo, the model show normal.

In the createLight function, I do a lot of tests by code from internet, I failed finally.
can anyone give me some help? thank you verty much!

My test code:

  int main(){

    osgViewer::Viewer viewer;
    osg::Node *animationNode = osgDB::readNodeFile("./dance.fbx");
    
    osg::ref_ptr<osg::Group> group = new osg::Group;
    group->addChild(animationNode);

    createLight(group, animationNode);
    
    viewer.setSceneData(group);
    return viewer.run();
  }

  bool createLight(osg::ref_ptr<osg::Group> lightRoot, osg::ref_ptr<osg::Node> node)
  {
    //开启光照
    lightRoot->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::ON);
    lightRoot->getOrCreateStateSet()->setMode(GL_LIGHT0, osg::StateAttribute::ON);

    //计算包围盒
    osg::BoundingSphere bs;
    node->computeBound();
    bs = node->getBound();

    //创建一个Light对象
    osg::ref_ptr<osg::Light> light = new osg::Light();
    light->setLightNum(0);
    //设置方向
    light->setDirection(osg::Vec3(0.0f, 0.0f, -1.0f));
    //设置位置
    light->setPosition(osg::Vec4(bs.center().x(), bs.center().y(), bs.center().z() + bs.radius(), 1.0f));
    //设置环境光的颜色
    light->setAmbient(osg::Vec4(1.0f, 1.0f, 1.0f, 1.0f));
    //设置散射光颜色
    light->setDiffuse(osg::Vec4(1.0f, 1.0f, 1.0f, 1.0f));

    //设置恒衰减指数
    light->setConstantAttenuation(1.0f);
    //设置线形衰减指数
    light->setLinearAttenuation(0.0f);
    //设置二次方衰减指数
    light->setQuadraticAttenuation(0.0f);

    //创建光源
    osg::ref_ptr<osg::LightSource> lightSource = new osg::LightSource();
    lightSource->setLight(light.get());

    lightRoot->addChild(lightSource.get());
    return true;
  }