GIS开发笔记（7）结合osg及osgEarth实现不同高度下的三个圆形区域形成的三维覆盖轮廓区域绘制

一、实现效果

二、实现原理
输入四个坐标点，第一个点为中心点，第二三四个点分别以中心点与地面垂线所在线上的各自高度水平面的交点为圆心旋转360°进行圆形区域绘制，然后将三个不同高度上的圆形区域进行结合形成三维覆盖区域的轮廓面。
三、参考代码

void GlobeWidget::draw3dCoverageRegion(const osg::ref_ptr<osg::Vec3Array>& points)
{if (!points || points->size() < 4)return;const osg::Vec3d& centerGeo = (*points)[0];osgEarth::GeoPoint geoCenter(osgEarth::SpatialReference::get("wgs84"),centerGeo.x(), centerGeo.y(), centerGeo.z(),osgEarth::ALTMODE_ABSOLUTE);osg::Vec3d centerWorld;geoCenter.toWorld(centerWorld);osg::Vec3d axis = centerWorld;axis.normalize();// === 圆形 ===const int segments = 60;  // 保证每个圆的分段数量一致std::vector<osg::ref_ptr<osg::Vec3Array>> circles;std::vector<int> layerOffsets;int vertexOffset = 0;// 绘制每个圆for (int i = 1; i <= 3; ++i){const osg::Vec3d& ptGeo = (*points)[i];osgEarth::GeoPoint geoPt(osgEarth::SpatialReference::get("wgs84"),ptGeo.x(), ptGeo.y(), ptGeo.z(),osgEarth::ALTMODE_ABSOLUTE);osg::Vec3d ptWorld;geoPt.toWorld(ptWorld);osg::Vec3d radiusVec = ptWorld - centerWorld;osg::ref_ptr<osg::Vec3Array> circlePts = new osg::Vec3Array();// 使用相同的分段数，避免缺口for (int j = 0; j < segments; ++j){double angle = osg::DegreesToRadians(360.0 * j / segments);osg::Matrixd rot = osg::Matrixd::rotate(angle, axis);osg::Vec3d rotated = radiusVec * rot;circlePts->push_back(centerWorld + rotated);}// 绘制当前圆osg::ref_ptr<osg::Geometry> circleGeom = new osg::Geometry();circleGeom->setVertexArray(circlePts);circleGeom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::LINE_LOOP, 0, circlePts->size()));osg::ref_ptr<osg::Vec4Array> circleColor = new osg::Vec4Array();circleColor->push_back(osg::Vec4(0.0, 1.0, 0.0, 1.0));circleGeom->setColorArray(circleColor, osg::Array::BIND_OVERALL);osg::ref_ptr<osg::Geode> circleGeode = new osg::Geode();circleGeode->addDrawable(circleGeom);m_userDrawGroup->addChild(circleGeode);circles.push_back(circlePts);layerOffsets.push_back(vertexOffset);vertexOffset += circlePts->size();}// === 轮廓面 ===osg::ref_ptr<osg::Vec3Array> meshVerts = new osg::Vec3Array();osg::ref_ptr<osg::DrawElementsUInt> meshIndices = new osg::DrawElementsUInt(GL_TRIANGLES);// 合并所有圆的顶点for (auto& c : circles){for (auto& pt : *c)meshVerts->push_back(pt);}// 连接每一层圆之间的三角形for (size_t i = 0; i < circles.size() - 1; ++i){const int offset0 = layerOffsets[i];const int offset1 = layerOffsets[i + 1];// 确保每层圆的点数一致const int count = segments;for (int j = 0; j < count - 1; ++j){// 创建三角形meshIndices->push_back(offset0 + j);meshIndices->push_back(offset1 + j);meshIndices->push_back(offset0 + j + 1);meshIndices->push_back(offset0 + j + 1);meshIndices->push_back(offset1 + j);meshIndices->push_back(offset1 + j + 1);}// 最后一个三角形：补全圆的缺口meshIndices->push_back(offset0 + count - 1);meshIndices->push_back(offset1 + count - 1);meshIndices->push_back(offset0);meshIndices->push_back(offset0);meshIndices->push_back(offset1 + count - 1);meshIndices->push_back(offset1);}osg::ref_ptr<osg::Geometry> meshGeom = new osg::Geometry();meshGeom->setVertexArray(meshVerts);meshGeom->addPrimitiveSet(meshIndices);osg::ref_ptr<osg::Vec4Array> meshColor = new osg::Vec4Array();meshColor->push_back(osg::Vec4(1.0, 1.0, 0.0, 0.4));  // 半透明黄色meshGeom->setColorArray(meshColor, osg::Array::BIND_OVERALL);meshGeom->getOrCreateStateSet()->setMode(GL_BLEND, osg::StateAttribute::ON);meshGeom->getOrCreateStateSet()->setRenderingHint(osg::StateSet::TRANSPARENT_BIN);meshGeom->getOrCreateStateSet()->setMode(GL_CULL_FACE, osg::StateAttribute::OFF);osg::ref_ptr<osg::Geode> meshGeode = new osg::Geode();meshGeode->addDrawable(meshGeom);m_userDrawGroup->addChild(meshGeode);// === 视角聚焦 ===if (m_osgWidget && m_osgWidget->getOsgViewer()){osgViewer::Viewer* viewer = m_osgWidget->getOsgViewer();osgEarth::Util::EarthManipulator* manip =dynamic_cast<osgEarth::Util::EarthManipulator*>(viewer->getCameraManipulator());if (manip){osgEarth::Viewpoint vp("Focus", centerGeo.x(), centerGeo.y(), centerGeo.z() + 300,0.0, -90.0, 1500.0);manip->setViewpoint(vp, 2.0);}}
}