三维场景动态生成正射纹理-框选区域拍照出图

       本文通过上节的人机交互形式获取模型拍照区域，采用添加Slave相机的形式实现框选区域拍照出图。

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目录

• 添加Slave相机，框选区域拍照出图

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内容

       在上期的RegionSelect中，将SlaveCamera初始化并添加到视图(viewer)中，在交互动作的最后，根据绘制的多边形调整SalveCamera的姿态，最后添加相机回调用于保存拍照后的纹理。

• 1 SalveCamera 初始化

    RegionSelect(osgViewer::Viewer* viewer, osgEarth::MapNode* mapNode)
    {
        ....
        ....
        ....

        _slaveCamera = new osg::Camera;
        {
            _slaveCamera->setReferenceFrame(osg::Camera::ABSOLUTE_RF);
            _slaveCamera->setClearColor(osg::Vec4d(0, 0, 0, 0));
            _slaveCamera->setComputeNearFarMode(osg::Camera::DO_NOT_COMPUTE_NEAR_FAR);
            _slaveCamera->setClearMask(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
            _slaveCamera->setRenderOrder(osg::Camera::PRE_RENDER);
            _slaveCamera->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER_OBJECT);
            //_imageGeneratorCamera->setImplicitBufferAttachmentMask(0, 0);
            _slaveCamera->dirtyAttachmentMap();
            _slaveCamera->attach(osg::Camera::COLOR_BUFFER0, _image.get());
            _slaveCamera->setSmallFeatureCullingPixelSize(-1.0f);
            _slaveCamera->setCullMask(~0u);
            double distance = 10;

            // set up a StateSet for the RTT camera.
            osg::StateSet* rttStateSet = _slaveCamera->getOrCreateStateSet();

            //rttStateSet->setAttributeAndModes(new osg::CullFace(osg::CullFace::BACK), osg::StateAttribute::ON | osg::StateAttribute::PROTECTED);
            osg::StateAttribute::OverrideValue forceOff =
                osg::StateAttribute::OFF | osg::StateAttribute::PROTECTED | osg::StateAttribute::OVERRIDE;
            rttStateSet->setMode(GL_DEPTH_TEST, osg::StateAttribute::ON | osg::StateAttribute::PROTECTED | osg::StateAttribute::OVERRIDE);
            rttStateSet->setRenderBinDetails(1003, "DepthSortedBin", osg::StateSet::OVERRIDE_RENDERBIN_DETAILS);

            //rttStateSet->setAttribute(new osg::Depth(osg::Depth::LEQUAL), osg::StateAttribute::ON | osg::StateAttribute::PROTECTED | osg::StateAttribute::OVERRIDE);
            //rttStateSet->setRenderBinDetails(10, "DepthSortedBin", osg::StateSet::OVERRIDE_RENDERBIN_DETAILS);
            //rttStateSet->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF);//关闭深度测试
            rttStateSet->setDefine(OE_LIGHTING_DEFINE, forceOff);
            //rttStateSet->addUniform( Registry::shaderFactory()->createUniformForGLMode(GL_LIGHTING, forceOff) );
            rttStateSet->setMode(GL_LIGHTING, forceOff);
        }
        _slaveCamera->setViewport(0, 0, _width, _height);
        viewer->addSlave(_slaveCamera);
    }

• 2  修改SlaveCamera姿态

      为了方便多边形框选工具的管理，可添加一个监视器实现多边形框选工具的装载与卸载。具体代码如下：

virtual void endhandle()
    {
        if (_feature->getGeometry()->size() < 3)
        {
            _feature->getGeometry()->clear();
            _worldPts.clear();
            _featureNode->dirty();
            return;
        }
        osg::ref_ptr<osg::Image> image;
        osg::Matrix world2TexMatrix;
        //orthoImageGenerator->RenderToImage(_worldPts, 0.1, image, world2TexMatrix);
        //osgDB::writeImageFile(*image, "C:/Users/CaiPing/Desktop/实体生成/test.jpg");
        {
            std::vector<osg::Vec3d> points;
            osg::ref_ptr<osgEarth::Polygon> polygon = (osgEarth::Polygon*)_feature->getGeometry();
            osg::Vec3d centerPoint;
            for (int i = 0; i < polygon->size(); i++)
            {
                points.push_back(polygon->at(i));
                centerPoint += (polygon->at(i) / polygon->size());
            }
            osg::Plane localPlane;
            PlaneFit(points, localPlane);
            double distance = 10;
            osg::Vec3d localNormal = osg::Vec3d(localPlane.asVec4()[0], localPlane.asVec4()[1], localPlane.asVec4()[2]);
            osg::Matrix toLocalPlaneMatrix = osg::Matrixd::translate(-points[0]) * osg::Matrix::rotate(localNormal, osg::Vec3d(0, 0, 1));
            osg::Vec3d localNorth = osg::Vec3d(0, 1, 0) * osg::Matrix::rotate(osg::Vec3d(0, 0, 1), localNormal);
            _slaveCamera->setViewMatrixAsLookAt(centerPoint + localNormal * distance, centerPoint, localNorth);

            osg::BoundingBox localBox;
            for (int i = 0; i < points.size(); i++)
            {
                osg::Vec3d tempPoint = points[i] * toLocalPlaneMatrix;
                localBox.expandBy(tempPoint);
            }
            _slaveCamera->setProjectionMatrixAsOrtho(localBox.xMin(), localBox.xMax(), localBox.yMin(), localBox.yMax(), 1, 200); //投影矩阵视图范围
            //_imageGeneratorCamera->setProjectionMatrixAsPerspective(45, 1.0*outImageWidth/ outImageHeight, 0, 500);
            _world2TexMatrix = _slaveCamera->getViewMatrix() * _slaveCamera->getProjectionMatrix();
            _slaveCamera->setPreDrawCallback(new Callback(this));

        }

• 3 相机回调保存纹理

 class Callback : public osg::Camera::DrawCallback
    {
    public:
        Callback(RegionSelect* regionSelect)
        {
            _regionSelect = regionSelect;
        }
        virtual void operator () (osg::RenderInfo& renderInfo) const
        {
            _regionSelect->writeOut();
        }
    protected:
        RegionSelect* _regionSelect;
};