osg三角带

案例1

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

osg::ref_ptr createQuad() {
    osg::ref_ptr geode = new osg::Geode;

    //创建一个用于保存几何信息的对象
    osg::ref_ptr geom = new osg::Geometry;

    //创建四个顶点的数组
    osg::ref_ptr v = new osg::Vec3Array;
    v->push_back(osg::Vec3(0.f, 0.f, 0.f));
    v->push_back(osg::Vec3(1.f, 0.f, 0.f));
    v->push_back(osg::Vec3(1.f, 0.f, 1.f));
    v->push_back(osg::Vec3(0.f, 0.f, 1.f));
    v->push_back(osg::Vec3(0.f, -1.f, 0.f));
    geom->setVertexArray(v.get());

    //创建四边形顶点索引数组，指定绘图基元为四边形，注意添加顺序
    osg::ref_ptr quad =
        new osg::DrawElementsUInt(osg::PrimitiveSet::QUADS, 0);
    quad->push_back(0);
    quad->push_back(1);
    quad->push_back(2);
    quad->push_back(3);

    //添加到几何体
    geom->addPrimitiveSet(quad.get());

    //创建三角形顶点索引数组，指定绘图基元为三角形
    osg::ref_ptr triangle =
        new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLES, 0);
    triangle->push_back(4);
    triangle->push_back(0);
    triangle->push_back(3);

    geom->addPrimitiveSet(triangle.get());



    //创建四个颜色的数组
    osg::ref_ptr c = new osg::Vec4Array;

    c->push_back(osg::Vec4(1.f, 0.f, 0.f, 1.f));
    c->push_back(osg::Vec4(0.f, 1.f, 0.f, 1.f));
    c->push_back(osg::Vec4(0.f, 0.f, 1.f, 1.f));
    c->push_back(osg::Vec4(1.f, 1.f, 0.f, 1.f));
    
    //创建颜色索引数组
    osg::TemplateIndexArray*
        colorIndex = new osg::TemplateIndexArray
        ();
    colorIndex->push_back(0);
    colorIndex->push_back(1);
    colorIndex->push_back(2);
    colorIndex->push_back(3);
    colorIndex->push_back(2);

    geom->setColorArray(c.get());
    geom->setColorBinding(osg::Geometry::BIND_PER_VERTEX);



    //为唯一的法线创建一个数组
    osg::ref_ptr n = new osg::Vec3Array;
    geom->setNormalArray(n.get());
    geom->setNormalBinding(osg::Geometry::BIND_OVERALL);
    n->push_back(osg::Vec3(0.f, -1.f, 0.f));


    //由保存的数据绘制四个顶点的多边形
    geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, 4));


    
    geode->addDrawable(geom.get());

    return geode.get();


}





int main()
{


    osg::ref_ptr viewer = new osgViewer::Viewer();

    osg::ref_ptr root = new osg::Group();

    root->addChild(createQuad());

    osgUtil::Optimizer opt;
    opt.optimize(root.get());

    viewer->setSceneData(root.get());
    viewer->realize();
    viewer->run();


}

案例二，绘制三角带

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 

//创建一个四边形节点
osg::ref_ptr createQuad() {
    //创建一个叶节点对象
    osg::ref_ptr geode = new osg::Geode();

    //创建一个几何体对象
    osg::ref_ptr geom = new osg::Geometry();

    //创建顶点数组，注意顶点的添加顺序是逆时针的
    osg::ref_ptr v = new osg::Vec3Array();
    //添加数据
    v->push_back(osg::Vec3(0.0f, 0.0f, 0.0f));
    v->push_back(osg::Vec3(1.0f, 0.0f, 0.0f));
    v->push_back(osg::Vec3(1.0f, 0.0f, 1.0f));
    v->push_back(osg::Vec3(0.0f, 0.0f, 1.0f));

    //设置顶点数据
    geom->setVertexArray(v.get());

    //创建纹理坐标
    osg::ref_ptr vt = new osg::Vec2Array();
    //添加数据
    vt->push_back(osg::Vec2(0.0f, 0.0f));
    vt->push_back(osg::Vec2(1.0f, 0.0f));
    vt->push_back(osg::Vec2(1.0f, 1.0f));
    vt->push_back(osg::Vec2(0.0f, 1.0f));


    //设置纹理坐标
    geom->setTexCoordArray(0, vt.get());

    osg::ref_ptr vc = new osg::Vec4Array();
    vc->push_back(osg::Vec4(1.0f, 0.0f, 0.0f, 1.0f));
    vc->push_back(osg::Vec4(0.0f, 1.0f, 0.0f, 1.0f));
    vc->push_back(osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f));
    vc->push_back(osg::Vec4(1.0f, 1.0f, 0.0f, 1.0f));

    //设置颜色数组
    geom->setColorArray(vc.get());
    //设置颜色的绑定方式为单个顶点
    geom->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
    
    //创建法线数组
    osg::ref_ptr nc = new osg::Vec3Array();
    //添加法线
    nc->push_back(osg::Vec3(0.0f, -1.0f, 0.0f));

    //设置法线数组
    geom->setNormalArray(nc.get());
    //设置法线的绑定方式去为全部顶点
    geom->setNormalBinding(osg::Geometry::BIND_OVERALL);

    //添加图元，绘图基元为四边形
    geom->addPrimitiveSet(new  osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, 4));
    return geom.get();

}


int main()
{


    osg::ref_ptr viewer = new osgViewer::Viewer();

    //方便查在多边形之间的切换，查看三角网
    viewer->addEventHandler(
        new osgGA::StateSetManipulator(viewer->getCamera()->getOrCreateStateSet()));

    osg::ref_ptr root = new osg::Group();

    osg::ref_ptr geo = createQuad();

    osgUtil::TriStripVisitor stripper;
    stripper.stripify(*(geo.get()));

    //添加到叶子节点
    osg::ref_ptr geode = new osg::Geode();
    geode->addDrawable(geo.get());

    root->addChild(geode.get());

    //优化场景数据
    osgUtil::Optimizer opt;
    opt.optimize(root.get());

    viewer->setSceneData(root.get());

    viewer->realize();

    viewer->run();

    return 0;
   

}