osg之基本图元（二）

一些顶点坐标与法向量的知识

osg::ref_ptr<osg::Node> CreateSimple()
{
   osg::ref_ptr<osg::Geode> geode=new osg::Geode;
   osg::ref_ptr<osg::Geometry> geometry=new osg::Geometry;

   //申请一些顶点
   osg::ref_ptr<osg::Vec3Array> coords=new osg::Vec3Array;
   //申请颜色
   osg::ref_ptr<osg::Vec4Array> colors=new osg::Vec4Array;
   //申请法向量
   osg::ref_ptr<osg::Vec3Array> normals=new osg::Vec3Array;

   geode->addDrawable(geometry);
   geode->getOrCreateStateSet()->setMode(GL_BLEND,osg::StateAttribute::ON);
   //设置顶点
   geometry->setVertexArray(coords);
   //设置顶点的关联方式
   geometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::Mode::QUADS,0,4));
   //设置顶点颜色
   geometry->setColorArray(colors);
   geometry->setColorBinding(osg::Geometry::AttributeBinding::BIND_PER_VERTEX);
   //设置法向量
   geometry->setNormalArray(normals);
   geometry->setNormalBinding(osg::Geometry::AttributeBinding::BIND_OVERALL);

   //设置顶点
   coords->push_back(osg::Vec3(-10.0,5.0,-10.0));
   coords->push_back(osg::Vec3(10.0,5.0,-10.0));
   coords->push_back(osg::Vec3(10.0,5.0,10.0));
   coords->push_back(osg::Vec3(-10.0,5.0,10.0));

   //颜色
   colors->push_back(osg::Vec4f(1.0,0.0,0.0,0.5));
   colors->push_back(osg::Vec4f(0.0,1.0,0.0,0.5));
   colors->push_back(osg::Vec4f(0.0,0.0,1.0,0.5));
   colors->push_back(osg::Vec4f(1.0,1.0,0.0,0.5));

   //压入一个法向量
   normals->push_back(osg::Vec3(0.0,-1.0,0.0));

   return geode;
}

int main()
{
  osg::ref_ptr<osgViewer::Viewer> viewer=new osgViewer::Viewer;
  osg::ref_ptr<osg::Group> group=new osg::Group;
  group->addChild(osgDB::readNodeFile("glider.osg"));
  group->addChild(CreateSimple());
  viewer->setSceneData(group);
  return viewer->run();
}