virtual void apply(osg::Geode& node) {for (int i = 0; i < node.getNumDrawables(); i++){osg::Geometry* geometry = dynamic_cast<osg::Geometry*>(node.getDrawable(i));if (geometry){//apply(*g);//***********************************************//解析頂點osg::Array* vertexArray = geometry->getVertexArray();if (vertexArray == NULL)return;//頂點數組osg::Vec3Array* verts = dynamic_cast<osg::Vec3Array*>(vertexArray);long lVertNum = verts->size();std::vector<osg::Vec3 >::iterator iter_ver = verts->begin();//遍歷頂點值for (; iter_ver != verts->end(); iter_ver++){double x = iter_ver->x();double y = iter_ver->y();double z = iter_ver->z();  }//紋理osg::Texture2D* tex2D = dynamic_cast<osg::Texture2D*>(geometry->getStateSet()->getTextureAttribute(0, osg::StateAttribute::TEXTURE));osg::Image* image = tex2D->getImage();osgDB::writeImageFile(*image, "abc.jpg");int width = image->s();int height = image->t();/*osg::Vec2 color;osg::Vec4 c = image->getColor(color);*///UVosg::Array* uvArry = geometry->getTexCoordArray(0);osg::Vec2Array* vertsUV = dynamic_cast<osg::Vec2Array*>(uvArry);std::vector<osg::Vec2 >::iterator iter_verUV = vertsUV->begin();std::vector<int> greenPointIndices;int i = 0;for (; iter_verUV != vertsUV->end(); iter_verUV++){double u = iter_verUV->x();double v = iter_verUV->y();osg::Vec2 color(u, v);osg::Vec4 c = image->getColor(color);float r = c.r() * 255;float g = c.g() * 255;float b = c.b() * 255;if (r < 100 && g < 100 && b < 100 )greenPointIndices.push_back(i);i++;}//索引int numP = geometry->getNumPrimitiveSets();osg::ref_ptr<osg::DrawElementsUInt> drawElemUInt = new osg::DrawElementsUInt(GL_TRIANGLES);for (unsigned int ipr = 0; ipr < numP; ipr++){osg::PrimitiveSet* prset = geometry->getPrimitiveSet(ipr);unsigned int ncnt = prset->getNumIndices();for (unsigned int ic = 0; ic * 3 < prset->getNumIndices(); ic++){unsigned int iIndex0 = prset->index(ic * 3);unsigned int iIndex1 = prset->index(ic * 3 + 1);unsigned int iIndex2 = prset->index(ic * 3 + 2);bool find = false;for (int i = 0; i < greenPointIndices.size(); i++){if (greenPointIndices[i] == iIndex0 || greenPointIndices[i] == iIndex1 || greenPointIndices[i] == iIndex2){find = true;break;}}if (find)continue;else{drawElemUInt->push_back(prset->index(ic * 3));drawElemUInt->push_back(prset->index(ic * 3 + 1));drawElemUInt->push_back(prset->index(ic * 3 + 2));}}}osg::ref_ptr<osg::Geometry> geometry_new = new osg::Geometry();geometry_new->setVertexArray(verts);geometry_new->getOrCreateStateSet()->setTextureAttributeAndModes(0, tex2D, osg::StateAttribute::ON);geometry_new->setTexCoordArray(0, uvArry);geometry_new->addPrimitiveSet(drawElemUInt);osg::Geode* pGeode_new = new osg::Geode;pGeode_new->removeDrawables(0, pGeode_new->getNumDrawables());pGeode_new->addDrawable(geometry_new);osgDB::writeNodeFile(*pGeode_new, "test.osgb", new osgDB::Options("WriteImageHint=IncludeData Compressor=zlib"));//***********************************************}}}

參考博主：osgb的頂點，紋理，索引，UV讀取與存儲_osgb獲取頂點-CSDN博客

作為C++小白看這段代碼的詳細解讀

這段代碼是用 C++ 編寫的，并使用了 OpenSceneGraph (OSG) —— 一個開源的高性能 3D 圖形引擎，廣泛用于地理信息系統、仿真、可視化等領域。

這段代碼定義了一個虛函數 apply(osg::Geode& node)，該函數的作用是：遍歷一個三維模型，識別紋理上顏色較暗的區域，剔除那些區域對應的三角形網格，然后將剩余的“亮色”區域導出為一個新的 3D 模型文件。

一、逐行詳細解析

開始遍歷Geode下的Drawable對象（通常是Geometry）

for (int i = 0; i < node.getNumDrawables(); i++)

遍歷Geode中所有的Drawable（通常是osg::Geometry類型）

處理每個Geometry

osg::Geometry* geometry = dynamic_cast<osg::Geometry*>(node.getDrawable(i));

嘗試將 Drawable 轉為 osg::Geometry 類型，如果轉換成功，表示該對象是幾何體。

解析頂點信息

osg::Array* vertexArray = geometry->getVertexArray();
osg::Vec3Array* verts = dynamic_cast<osg::Vec3Array*>(vertexArray);

獲取頂點數組并強制轉換為三維坐標數組（Vec3Array）

vert存儲所有頂點坐標

for (; iter_ver != verts->end(); iter_ver++)
{double x = iter_ver->x();double y = iter_ver->y();double z = iter_ver->z();  
}

遍歷每個頂點，獲取其三維坐標（這里沒做實際操作）

提取紋理圖像

osg::Texture2D* tex2D = dynamic_cast<osg::Texture2D*>(geometry->getStateSet()->getTextureAttribute(0, ...));
osg::Image* image = tex2D->getImage();
osgDB::writeImageFile(*image, "abc.jpg");

獲取貼在模型上的紋理（Texture2D）

提取出其中的圖像（osg::Image）

保存圖像為JPG文件（調試用途）

讀取UV坐標+獲取紋理顏色

osg::Array* uvArry = geometry->getTexCoordArray(0);
osg::Vec2Array* vertsUV = dynamic_cast<osg::Vec2Array*>(uvArry);

獲取紋理坐標（UV）數組

for (; iter_verUV != vertsUV->end(); iter_verUV++)
{double u = iter_verUV->x();double v = iter_verUV->y();osg::Vec2 color(u, v);osg::Vec4 c = image->getColor(color);...
}

遍歷每個頂點對應的紋理坐標（u,v）

從image圖像中獲取對應像素顏色c

判斷顏色是否“偏暗”，若R、G、B分量都小于100（即為暗色或黑色點）

if (r < 100 && g < 100 && b < 100)greenPointIndices.push_back(i);

這些“暗黑點”會被記錄到greenPointIndices中

處理索引，剔除包含暗黑點的三角面

osg::DrawElementsUInt* drawElemUInt = new osg::DrawElementsUInt(GL_TRIANGLES);

新建一個DrawElementsUInt類型的三角形集合，保存有效三角面索引。

for (ipr ...)
{for (ic ...){unsigned int iIndex0 = prset->index(ic * 3);...if (任意一個頂點是暗色點)continue;elsedrawElemUInt->push_back(三個頂點索引);}
}

遍歷所有原始三角形

若三角形中有任意一個頂點在greenPointIndices中（即暗點），跳過不加入新網格。

其他三角面則加入drawElemUInt

構建新Geometry并導出為OSGB文件

osg::Geometry* geometry_new = new osg::Geometry();
geometry_new->setVertexArray(verts);
...
geometry_new->addPrimitiveSet(drawElemUInt);

構建一個新幾何體，復用原始頂點和紋理坐標，僅替換三角面為“亮色區域”

osg::Geode* pGeode_new = new osg::Geode;
pGeode_new->addDrawable(geometry_new);
osgDB::writeNodeFile(*pGeode_new, "test.osgb", ...);

將新的幾何體寫入.osgb文件（OpenSceneGraph二進制模式格式）