OpenSceneGraph (OSG) 提供了多种方式来生成和导出3D数据格式文件。以下是详细的生成方法和示例代码：
一、基本文件生成方法
1. 使用osgDB::writeNodeFile函数
这是最直接的生成方式，支持多种格式：
#include <osgDB/WriteFile>osg::ref_ptr<osg::Node> scene = createScene(); // 创建你的场景图// 导出为不同格式
bool success;
success = osgDB::writeNodeFile(*scene, "output.osgt"); // OSG文本格式
success = osgDB::writeNodeFile(*scene, "output.osgb"); // OSG二进制格式
success = osgDB::writeNodeFile(*scene, "output.obj"); // Wavefront OBJ
success = osgDB::writeNodeFile(*scene, "output.dae"); // COLLADA
success = osgDB::writeNodeFile(*scene, "output.fbx"); // FBX(需插件支持)2. 支持的导出格式
| 格式类型 | 文件扩展名 | 说明 |
|---|---|---|
| OSG原生 | .osgt, .osgb, .osgx | 文本/二进制/XML格式 |
| 通用3D | .obj, .stl, .ply | 静态网格格式 |
| 场景格式 | .dae, .fbx, .3ds | 支持完整场景 |
| 地形数据 | .ive, .lwo, .txp | 优化格式 |
二、编程生成场景并导出
1. 创建简单几何体并导出
#include <osg/Geode>
#include <osg/Geometry>
#include <osgDB/WriteFile>osg::Geode* createCube() {osg::ref_ptr<osg::Geode> geode = new osg::Geode;osg::ref_ptr<osg::Geometry> geometry = new osg::Geometry;// 定义8个顶点（立方体）osg::Vec3Array* vertices = new osg::Vec3Array;vertices->push_back(osg::Vec3(-1.0f, -1.0f, 1.0f)); // 前左下vertices->push_back(osg::Vec3( 1.0f, -1.0f, 1.0f)); // 前右下vertices->push_back(osg::Vec3( 1.0f, 1.0f, 1.0f)); // 前右上vertices->push_back(osg::Vec3(-1.0f, 1.0f, 1.0f)); // 前左上vertices->push_back(osg::Vec3(-1.0f, -1.0f, -1.0f)); // 后左下vertices->push_back(osg::Vec3( 1.0f, -1.0f, -1.0f)); // 后右下vertices->push_back(osg::Vec3( 1.0f, 1.0f, -1.0f)); // 后右上vertices->push_back(osg::Vec3(-1.0f, 1.0f, -1.0f)); // 后左上geometry->setVertexArray(vertices);// 定义法线osg::Vec3Array* normals = new osg::Vec3Array;normals->push_back(osg::Vec3( 0.0f, 0.0f, 1.0f)); // 前normals->push_back(osg::Vec3( 0.0f, 0.0f, -1.0f)); // 后normals->push_back(osg::Vec3( 1.0f, 0.0f, 0.0f)); // 右normals->push_back(osg::Vec3(-1.0f, 0.0f, 0.0f)); // 左normals->push_back(osg::Vec3( 0.0f, 1.0f, 0.0f)); // 上normals->push_back(osg::Vec3( 0.0f, -1.0f, 0.0f)); // 下geometry->setNormalArray(normals, osg::Array::BIND_PER_PRIMITIVE);// 定义6个面（12个三角形）osg::DrawElementsUInt* faces = new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLES, 0);// 前面faces->push_back(0); faces->push_back(1); faces->push_back(2);faces->push_back(2); faces->push_back(3); faces->push_back(0);// 后面faces->push_back(5); faces->push_back(4); faces->push_back(7);faces->push_back(7); faces->push_back(6); faces->push_back(5);// 右面faces->push_back(1); faces->push_back(5); faces->push_back(6);faces->push_back(6); faces->push_back(2); faces->push_back(1);// 左面faces->push_back(4); faces->push_back(0); faces->push_back(3);faces->push_back(3); faces->push_back(7); faces->push_back(4);// 上面faces->push_back(3); faces->push_back(2); faces->push_back(6);faces->push_back(6); faces->push_back(7); faces->push_back(3);// 下面faces->push_back(4); faces->push_back(5); faces->push_back(1);faces->push_back(1); faces->push_back(0); faces->push_back(4);geometry->addPrimitiveSet(faces);geode->addDrawable(geometry);return geode.release();
}int main() {osg::ref_ptr<osg::Node> scene = createCube();osgDB::writeNodeFile(*scene, "box.osgb");return 0;
}2. 生成带纹理的模型
osg::Node* createTexturedQuad() {osg::ref_ptr<osg::Geode> geode = new osg::Geode;osg::ref_ptr<osg::Geometry> geom = new osg::Geometry;// 顶点osg::Vec3Array* vertices = new osg::Vec3Array;vertices->push_back(osg::Vec3(-1,0,-1));vertices->push_back(osg::Vec3(1,0,-1));vertices->push_back(osg::Vec3(1,0,1));vertices->push_back(osg::Vec3(-1,0,1));geom->setVertexArray(vertices);// 纹理坐标osg::Vec2Array* texcoords = new osg::Vec2Array;texcoords->push_back(osg::Vec2(0,0));texcoords->push_back(osg::Vec2(1,0));texcoords->push_back(osg::Vec2(1,1));texcoords->push_back(osg::Vec2(0,1));geom->setTexCoordArray(0, texcoords);// 加载纹理osg::ref_ptr<osg::Texture2D> texture = new osg::Texture2D;texture->setImage(osgDB::readImageFile("texture.jpg"));// 创建状态集osg::ref_ptr<osg::StateSet> stateset = geom->getOrCreateStateSet();stateset->setTextureAttributeAndModes(0, texture, osg::StateAttribute::ON);geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, 4));geode->addDrawable(geom);return geode.release();
}三、高级导出选项
1. 使用osg::Options控制导出
osg::ref_ptr<osgDB::Options> options = new osgDB::Options;
options->setOptionString("WriteImageHint=IncludeFile"); // 包含纹理引用osgDB::writeNodeFile(*scene, "textured_model.osgt", options.get());2. 常用导出选项
| 选项字符串 | 功能描述 |
|---|---|
| "WriteImageHint=IncludeFile" | 包含纹理文件引用 |
| "Compressor=zlib" | 使用压缩格式 |
| "Precision=15" | 设置浮点精度 |
| "OutputTextureFiles" | 导出纹理文件 |
3. 批量导出多个LOD级别
void exportLODs(osg::Node* model, const std::string& basename) {osg::ref_ptr<osg::LOD> lod = new osg::LOD;// 创建不同细节级别的模型osg::Node* highRes = createSimplifiedModel(model, 1.0f);osg::Node* medRes = createSimplifiedModel(model, 0.5f);osg::Node* lowRes = createSimplifiedModel(model, 0.2f);lod->addChild(highRes, 0, 50);lod->addChild(medRes, 50, 200);lod->addChild(lowRes, 200, FLT_MAX);osgDB::writeNodeFile(*lod, basename + "_lod.osgb");
}// 辅助函数：创建简化模型
osg::Node* createSimplifiedModel(osg::Node* original, float ratio) {osgUtil::Simplifier simplifier(ratio);osg::ref_ptr<osg::Node> copy = dynamic_cast<osg::Node*>(original->clone(osg::CopyOp::DEEP_COPY_ALL));copy->accept(simplifier);return copy.release();
}四、处理导出问题
1. 检查插件支持
// 列出所有支持的写入格式
osgDB::Registry::instance()->getWriterExtensions();// 检查特定格式是否支持
if (osgDB::Registry::instance()->getReaderWriterForExtension("fbx")) {// FBX导出可用
}2. 错误处理
bool result = osgDB::writeNodeFile(*node, "output.fbx");
if (!result) {OSG_WARN << "Failed to export FBX file. Make sure FBX plugin is installed." << std::endl;// 尝试回退格式osgDB::writeNodeFile(*node, "output.obj");
}五、实际应用示例
1. 生成地形并导出
osg::Node* createTerrain() {osg::ref_ptr<osg::HeightField> hf = new osg::HeightField;hf->allocate(64, 64); // 64x64网格// 填充高度数据for (unsigned int r=0; r<hf->getNumRows(); ++r) {for (unsigned int c=0; c<hf->getNumColumns(); ++c) {float height = sin(c/10.0f) * cos(r/10.0f) * 10.0f;hf->setHeight(c, r, height);}}osg::ref_ptr<osg::Geode> geode = new osg::Geode;geode->addDrawable(new osg::ShapeDrawable(hf.get()));return geode.release();
}// 导出为OpenFlight格式
osgDB::writeNodeFile(*createTerrain(), "terrain.flt");2. 动画模型导出
osg::AnimationPath* createAnimationPath() {osg::ref_ptr<osg::AnimationPath> path = new osg::AnimationPath;path->setLoopMode(osg::AnimationPath::LOOP);float time = 0.0f;float delta = 1.0f/30.0f; // 30fpsfor (unsigned int i=0; i<60; ++i) {osg::Vec3 pos(sin(time), cos(time), 0.0f);path->insert(time, osg::AnimationPath::ControlPoint(pos));time += delta;}return path.release();
}osg::Node* createAnimatedModel() {osg::ref_ptr<osg::MatrixTransform> animNode = new osg::MatrixTransform;animNode->setUpdateCallback(new osg::AnimationPathCallback(createAnimationPath()));// 添加你的模型animNode->addChild(createSimpleBox());return animNode.release();
}// 导出动画模型
osgDB::writeNodeFile(*createAnimatedModel(), "animated.dae");
