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毕业设计网页设计论文,乐陵市seo关键词优化,姓氏变logo设计免费生成,哪个网站可以查公司注册信息OSG中实现3D世界坐标到2D屏幕坐标的转换是许多应用的基础功能，如HUD显示、对象拾取等。以下是详细的实现方法： 1. 基本坐标转换原理 3D到2D坐标转换流程图： 2D到3D坐标转换流程图： 2. 核心转换方法 2.1 使用osg::Matrix实现转换…

OSG中实现3D世界坐标到2D屏幕坐标的转换是许多应用的基础功能，如HUD显示、对象拾取等。以下是详细的实现方法：

1. 基本坐标转换原理

3D到2D坐标转换流程图：

2D到3D坐标转换流程图：

2. 核心转换方法

2.1 使用osg::Matrix实现转换

// 3D世界坐标转2D屏幕坐标
bool worldToScreen(const osg::Vec3& worldPos, osg::Vec3& screenPos, const osg::Camera* camera)
{// 获取视图矩阵、投影矩阵和视口const osg::Matrix& viewMatrix = camera->getViewMatrix();const osg::Matrix& projMatrix = camera->getProjectionMatrix();const osg::Viewport* viewport = camera->getViewport();if(!viewport) return false;// 执行坐标转换osg::Vec3 eyePos = worldPos * viewMatrix;osg::Vec3 clipPos = eyePos * projMatrix;// 归一化设备坐标(NDC)osg::Vec3 ndcPos;ndcPos.x() = clipPos.x() / clipPos.w();ndcPos.y() = clipPos.y() / clipPos.w();ndcPos.z() = clipPos.z() / clipPos.w();// 转换为屏幕坐标screenPos.x() = (ndcPos.x() * 0.5f + 0.5f) * viewport->width() + viewport->x();screenPos.y() = (ndcPos.y() * 0.5f + 0.5f) * viewport->height() + viewport->y();screenPos.z() = (ndcPos.z() * 0.5f + 0.5f);// 检查点是否在视锥体内return (ndcPos.x() >= -1.0f && ndcPos.x() <= 1.0f &&ndcPos.y() >= -1.0f && ndcPos.y() <= 1.0f &&ndcPos.z() >= -1.0f && ndcPos.z() <= 1.0f);
}

2.2 使用osgUtil::SceneView简化转换

osg::Vec3 worldToScreen(osg::Vec3 worldPos, osgUtil::SceneView* sceneView)
{osg::Matrix MVPW = sceneView->getProjectionMatrix() * sceneView->getViewMatrix() * osg::Matrix::identity();osg::Viewport* viewport = sceneView->getViewport();osg::Vec3 screenPos = worldPos * MVPW;// 透视除法screenPos.x() = (screenPos.x() / screenPos.z() * 0.5f + 0.5f) * viewport->width() + viewport->x();screenPos.y() = (screenPos.y() / screenPos.z() * 0.5f + 0.5f) * viewport->height() + viewport->y();return screenPos;
}

3. 2D到3D坐标转换（逆向）

// 2D屏幕坐标转3D世界坐标（获取地面交点）
bool screenToWorld(const osg::Vec3& screenPos, osg::Vec3& worldPos, const osg::Camera* camera, const osg::Vec3& planeNormal, float planeDistance)
{if(!camera || !camera->getViewport()) return false;// 创建从屏幕到世界的射线osg::Matrix VPW = camera->getViewport()->computeWindowMatrix();osg::Matrix inverseMVPW = osg::Matrix::inverse(camera->getViewMatrix() * camera->getProjectionMatrix() * VPW);// 近平面和远平面点osg::Vec3 nearPoint = osg::Vec3(screenPos.x(), screenPos.y(), 0.0f) * inverseMVPW;osg::Vec3 farPoint = osg::Vec3(screenPos.x(), screenPos.y(), 1.0f) * inverseMVPW;// 计算与指定平面的交点osg::Plane plane(planeNormal, planeDistance);return plane.intersect(nearPoint, farPoint, worldPos);
}

4. 实际应用示例

4.1 在3D对象上显示2D标签

class LabelUpdateCallback : public osg::NodeCallback {
public:LabelUpdateCallback(osgText::Text* label, osg::Node* target, osg::Camera* camera): _label(label), _target(target), _camera(camera) {}virtual void operator()(osg::Node* node, osg::NodeVisitor* nv) {// 获取目标的世界坐标osg::Matrix worldMat = _target->getWorldMatrices()[0];osg::Vec3 worldPos = osg::Vec3(0,0,0) * worldMat;// 转换为屏幕坐标osg::Vec3 screenPos;if(worldToScreen(worldPos, screenPos, _camera)) {_label->setPosition(osg::Vec3(screenPos.x(), screenPos.y(), 0));_label->setNodeMask(0xFFFFFFFF); // 显示} else {_label->setNodeMask(0x0); // 隐藏}traverse(node, nv);}private:osg::ref_ptr<osgText::Text> _label;osg::ref_ptr<osg::Node> _target;osg::ref_ptr<osg::Camera> _camera;
};

4.2 实现3D对象的屏幕空间固定效果

osg::Camera* createHUDCamera(osgViewer::Viewer* viewer)
{// 创建HUD相机osg::Camera* camera = new osg::Camera;camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);camera->setProjectionMatrix(osg::Matrix::ortho2D(0, viewer->getCamera()->getViewport()->width(), 0, viewer->getCamera()->getViewport()->height()));camera->setViewMatrix(osg::Matrix::identity());camera->setClearMask(GL_DEPTH_BUFFER_BIT);camera->setRenderOrder(osg::Camera::POST_RENDER);camera->setAllowEventFocus(false);return camera;
}void addScreenFixedNode(osg::Group* root, osgViewer::Viewer* viewer, osg::Node* node, const osg::Vec3& screenPos)
{osg::Camera* hudCamera = createHUDCamera(viewer);// 更新回调保持屏幕位置node->setUpdateCallback(new ScreenPositionCallback(viewer->getCamera(), screenPos));hudCamera->addChild(node);root->addChild(hudCamera);
}

5. 高级应用：拾取(Picking)实现

class PickHandler : public osgGA::GUIEventHandler {
public:bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa) {if(ea.getEventType() != osgGA::GUIEventAdapter::RELEASE || ea.getButton() != osgGA::GUIEventAdapter::LEFT_MOUSE_BUTTON)return false;osgViewer::View* view = dynamic_cast<osgViewer::View*>(&aa);if(!view) return false;// 2D屏幕坐标转3D世界射线osgUtil::LineSegmentIntersector::Intersections intersections;if(view->computeIntersections(ea.getX(), ea.getY(), intersections)) {for(auto& hit : intersections) {osg::Vec3 worldPos = hit.getWorldIntersectPoint();osg::Vec3 screenPos;// 3D到2D转换验证worldToScreen(worldPos, screenPos, view->getCamera());std::cout << "Picked at: World(" << worldPos << ") Screen(" << screenPos.x() << "," << screenPos.y() << ")\n";}}return true;}
};