OSG学习笔记（三）之如何将非三角面转换为三角面

来源：互联网发布：淘宝小号批量注册编辑：程序博客网时间：2024/05/04 08:37

在使用OSG开发中，需要将OSG对应的三维模型转换为自己的模型，为了方便少出错，三角面是一个不错的选择（对于之支持三角面绘制的这点显得更重要），研究了下OSG，发现osg::TriangleFunctor这个模板可以实现我们想要的功能，用户使用的时候首先要重载operator（）方法，然后调用geometry->accept（）实现对其拆分。具体实现如下：

1.重载operator（）方法

struct MyVecter{void operator() (const osg::Vec3& v1, const osg::Vec3& v2, const osg::Vec3& v3, bool) const{arrList->push_back(v1);arrList->push_back(v2);arrList->push_back(v3);}osg::Vec3Array* arrList;};

2.转换为三角面

osg::TriangleFunctor<MyVecter> tf;tf.arrList = new osg::Vec3Array;geometry->accept(tf);

下面将给出一个简单的案例：构造一个四边面，然后转换为三角面

#include <osg/Geode>#include <osg/Geometry>#include <osg/Vec3>#include <osg/TriangleFunctor>#include <osgDB/ReadFile>#include <osgViewer/Viewer>#include <iostream>#include <vector>using namespace std;struct MyVecter{void operator() (const osg::Vec3& v1, const osg::Vec3& v2, const osg::Vec3& v3, bool) const{arrList->push_back(v1);arrList->push_back(v2);arrList->push_back(v3);}osg::Vec3Array* arrList;};void PrintTriangles(osg::TriangleFunctor<MyVecter> tf){int nCont = tf.arrList->size();vector<osg::Vec3f> arrVec = tf.arrList->asVector();for (int i = 0; i < nCont; i++){osg::Vec3f v = arrVec[i];cout << "X:" << v[0] <<" Y:" << v[1] << " Z:" << v[2] << endl;}}osg::ref_ptr<osg::Node> createScene(){osg::ref_ptr<osg::Geometry> polyGeom = new osg::Geometry;osg::Vec3 myCoords[] ={osg::Vec3(0.0247182, 0.0f, -0.156548),osg::Vec3(0.0247182, 0.0f, -0.00823939),osg::Vec3(-0.160668, 0.0f, -0.0453167),osg::Vec3(-0.222464, 0.0f, -0.13183),osg::Vec3(0.238942, 0.0f, -0.251302),osg::Vec3(0.333696, 0.0f, 0.0329576),osg::Vec3(0.164788, 0.0f, -0.0453167),osg::Vec3(0.13595,  0.0f, -0.255421)};int numCoords = sizeof(myCoords)/sizeof(osg::Vec3);osg::Vec3Array* vertices = new osg::Vec3Array(numCoords, myCoords);polyGeom->setVertexArray(vertices);osg::ref_ptr<osg::Vec4Array> shared_colors = new osg::Vec4Array;shared_colors->push_back(osg::Vec4(1.0f,1.0f,0.0f,1.0f));polyGeom->setColorArray(shared_colors.get(), osg::Array::BIND_OVERALL);osg::ref_ptr<osg::Vec3Array> shared_normals = new osg::Vec3Array;shared_normals->push_back(osg::Vec3(0.0f,-1.0f,0.0f));polyGeom->setNormalArray(shared_normals.get(), osg::Array::BIND_OVERALL);polyGeom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, numCoords));osg::TriangleFunctor<MyVecter> tf;tf.arrList = new osg::Vec3Array;polyGeom->accept(tf);PrintTriangles(tf);//向geode类添加几何体osg::ref_ptr<osg::Geode> geode = new osg::Geode;geode->addDrawable(polyGeom);return geode;}int main(){osg::Group* root = new osg::Group;root->addChild( createScene() );osgViewer::Viewer viewer;viewer.setSceneData( root );return viewer.run();}

注意：本案例只是将四边面转换为三角面打印出来，并没有设置到geometry中去。

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