添加osgEarth创建六边形网格文章

.gitignore

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+.vscode/settings.json

blog/assets/osgEarth六边形网格/2dmap.earth

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+<?xml version="1.0" ?>
+
+<map name = "ddmap" type="projected" version="2">
+  <options>
+	<terrain driver = "rex" lighting = "true" skirt_ratio="0.05" min_tile_range_factor = "6" first_lod = "0" blending = "false" color = "#ffffffff" tile_size = "17" normalize_edges = "true" compress_normal_maps = "false" normal_maps = "true" min_expiry_frames = "0" min_expiry_time = "0"/>
+    <!-- <profile>plate-carre</profile> -->
+    <profile>spherical-mercator</profile>
+  </options>
+
+  <image name="world" driver="tms" opacity = "1.0"  format="png">
+    <url>E:/GISData/Imagery/tms.xml</url>
+  </image>
+
+</map>

blog/osgEarth六边形网格.md

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+# osgEarth构建六边形网格兵棋地图示例
+
+　　在osgEarth中添加了osg::Geode，绘制蜂窝状六边形网格效果，包括墨卡托平面地图，地理坐标平面地图，三维地球等多种模式
+![alt text](assets/osgEarth六边形网格/image.png)
+```c++
+// 函数：创建六边形蜂窝网格线，三维地球
+osg::ref_ptr<osg::Geometry> createHexagonWireframe(const osgEarth::GeoExtent& extent, float radius, int rows, int cols) {
+	osg::ref_ptr<osg::Geometry> geometry = new osg::Geometry;
+
+	osg::ref_ptr<osg::Vec3Array> vertices = new osg::Vec3Array;
+
+	auto fromSRS = osgEarth::SpatialReference::get("wgs84");
+	auto srs = extent.getSRS();
+
+	// 计算每个六边形中心点的地理坐标
+	float height = std::sqrt(3.0f) * radius;
+	float lonDelta = radius;// extent.width() / cols;
+	float latDelta = radius;// extent.height() / rows;
+	for (int row = 0; row < rows; ++row) {
+		for (int col = 0; col < cols; ++col) {
+
+			float lonDelta = col * 1.5f * radius;
+			float latDelta = row * height;
+			if (col % 2 == 1)
+				latDelta += height / 2.0f;
+
+			float lon = 108.0 + lonDelta;
+			float lat = 35.0 + latDelta;
+			osg::Vec3d centerGeo(lon, lat, 3000.0);
+
+			// 计算六边形的顶点
+			for (int i = 0; i < 6; ++i) 
+			{
+				float angle = osg::PI * 2.0f * float(i) / 6.0f;
+				float x = radius * std::cos(angle);
+				float y = radius * std::sin(angle);
+				osg::Vec3d vertexXYZ;
+				osgEarth::GeoPoint pppp(fromSRS, osg::Vec3d(lon + x, lat + y, 1.0));
+				pppp.transformInPlace(srs);
+				pppp.toWorld(vertexXYZ);
+				//vertices->push_back(centerXYZ + vertexXYZ - centerGeo);
+				vertices->push_back(vertexXYZ);
+			}
+		}
+	}
+
+	geometry->setVertexArray(vertices);
+
+	osg::ref_ptr<osg::DrawElementsUInt> indices = new osg::DrawElementsUInt(GL_LINES);
+	int numHexagons = rows * cols;
+
+	for (int i = 0; i < numHexagons; ++i) {
+		int offset = i * 6;
+		for (int j = 0; j < 6; ++j) {
+			indices->push_back(offset + j);
+			indices->push_back(offset + (j + 1) % 6);
+		}
+	}
+
+	geometry->addPrimitiveSet(indices);
+
+	// 启用 VBO
+	geometry->setUseVertexBufferObjects(true);
+
+	// 设置线宽
+	osg::ref_ptr<osg::StateSet> stateSet = geometry->getOrCreateStateSet();
+	osg::ref_ptr<osg::LineWidth> lineWidth = new osg::LineWidth(1.0f); // 设置线宽为 1.0
+	stateSet->setAttributeAndModes(lineWidth, osg::StateAttribute::ON);
+
+	return geometry;
+}
+
+
+// 函数：创建六边形蜂窝网格线,平面地图
+osg::ref_ptr<osg::Geometry> createHexagonWireframe(double startX,double startY, float radius, int rows, int cols) {
+	osg::ref_ptr<osg::Geometry> geometry = new osg::Geometry;
+
+	osg::ref_ptr<osg::Vec3Array> vertices = new osg::Vec3Array;
+
+
+	// 计算每个六边形中心点的地理坐标
+	float height = std::sqrt(3.0f) * radius;
+	for (int row = 0; row < rows; ++row) 
+	{
+		for (int col = 0; col < cols; ++col) 
+		{
+			float xDelta = col * 1.5f * radius;
+			float yDelta = row * height;
+			if (col % 2 == 1)
+				yDelta += height / 2.0f;
+
+			float lon = startX + xDelta;
+			float lat = startY + yDelta;
+
+			// 计算六边形的顶点
+			for (int i = 0; i < 6; ++i)
+			{
+				float angle = osg::PI * 2.0f * float(i) / 6.0f;
+				float x = radius * std::cos(angle);
+				float y = radius * std::sin(angle);
+				//vertices->push_back(centerXYZ + vertexXYZ - centerGeo);
+				vertices->push_back(osg::Vec3d(lon + x, lat + y, 1.0));
+			}
+		}
+	}
+
+	geometry->setVertexArray(vertices);
+
+	osg::ref_ptr<osg::DrawElementsUInt> indices = new osg::DrawElementsUInt(GL_LINES);
+	int numHexagons = rows * cols;
+
+	for (int i = 0; i < numHexagons; ++i) {
+		int offset = i * 6;
+		for (int j = 0; j < 6; ++j) {
+			indices->push_back(offset + j);
+			indices->push_back(offset + (j + 1) % 6);
+		}
+	}
+
+	geometry->addPrimitiveSet(indices);
+
+	// 启用 VBO
+	geometry->setUseVertexBufferObjects(true);
+
+	// 设置线宽
+	osg::ref_ptr<osg::StateSet> stateSet = geometry->getOrCreateStateSet();
+	osg::ref_ptr<osg::LineWidth> lineWidth = new osg::LineWidth(1.0f); // 设置线宽为 1.0
+	stateSet->setAttributeAndModes(lineWidth, osg::StateAttribute::ON);
+
+	return geometry;
+}
+
+
+int main(int argc, char* argv[])
+{
+	auto ddMap = osgDB::readNodeFile("E:/GISData/Imagery/2dmap.earth");
+
+	auto mapNode = osgEarth::MapNode::findMapNode(ddMap);
+
+	osgEarth::GeoPoint start(osgEarth::SpatialReference::get("wgs84"), 108.0, 35.0);
+	start.transformInPlace(mapNode->getMapSRS());
+
+	auto hexagon222 = createHexagonWireframe(start.x(), start.y()
+		, 500, 100, 100);
+
+	hexagon222->getOrCreateStateSet()->setAttribute(new osg::Depth(osg::Depth::ALWAYS, 0.0, 1.0, false), osg::StateAttribute::ON);
+	osgEarth::GLUtils::setLighting(hexagon222->getOrCreateStateSet(), osg::StateAttribute::OFF);
+
+	mapNode->addChild(hexagon222);
+
+	auto m = new osgEarth::EarthManipulator;
+
+	osgViewer::Viewer viewer;
+	viewer.setSceneData(ddMap);
+	
+	viewer.setCameraManipulator(m);
+	viewer.getCamera()->addCullCallback(new osgEarth::AutoClipPlaneCullCallback(mapNode));
+
+	viewer.realize();
+
+
+	m->setViewpoint(osgEarth::Viewpoint("", 108, 35, 0.0, 0.0, -89.9, 100000));
+
+	return viewer.run();
+}
+```
+
+## 附件
+[2dmap.earth](./assets/osgEarth六边形网格/2dmap.earth)
+
+## 性能问题
+ * 考虑使用instanced drawing
+ * 使用kd-tree
+ * ...