[osg-users] How to properly update a Geometry

[Glenn Waldron]

If you're just updating an existing array, you don't need to call
setVertexArray (etc); but you need to mark it dirty by calling

  m_vertices->dirty();

That applies also to your other buffer objects (color array, elements, etc.)


Glenn Waldron

On Thu, Apr 28, 2016 at 3:51 PM, Daniel Neos <daniel.rd at hotmail.de> wrote:

> Greetings everyone,
>
> I am trying to display a point cloud, consisting of vertices and color
> with OpenSceneGraph. A static point cloud to display is rather easy with
> this guide.
> But I am not capable of updating such a point cloud. My intention is to
> create a geometry and attach it to my viewer class once.
> This is the mentioned method which is called once in the beginning.
>
> The OSGWidget strongly depends on this OpenGLWidget based approach.
>
>
> Code:
>
> void OSGWidget::attachGeometry(osg::ref_ptr<osg::Geometry> geom)
> {
> osg::Geode* geode = new osg::Geode;
>
> geom->setDataVariance(osg::Object::DYNAMIC);
> geom->setUseDisplayList(false);
> geom->setUseVertexBufferObjects(true);
> bool addDrawSuccess = geode->addDrawable(geom.get()); // Adding Drawable
> Shape to the geometry node
>
>
> if (!addDrawSuccess)
> {
> throw "Adding Drawable failed!";
> }
>
> osg::StateSet* stateSet = geode->getOrCreateStateSet();
> stateSet->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
>
>
> float aspectRatio = static_cast<float>(this->width()) /
> static_cast<float>(this->height());
>
> // Setting up the camera
> osg::Camera* camera = new osg::Camera;
> camera->setViewport(0, 0, this->width(), this->height());
> camera->setClearColor(osg::Vec4(0.f, 0.f, 0.f, 1.f)); // Kind of
> Backgroundcolor, clears the buffer and sets the default color (RGBA)
> camera->setProjectionMatrixAsPerspective(30.f, aspectRatio, 1.f, 1000.f);
> // Create perspective projection
> camera->setGraphicsContext(graphicsWindow_); // embed
>
> osgViewer::View* view = new osgViewer::View;
> view->setCamera(camera); // Set the defined camera
> view->setSceneData(geode); // Set the geometry
> view->addEventHandler(new osgViewer::StatsHandler);
>
>
> osgGA::TrackballManipulator* manipulator = new osgGA::TrackballManipulator;
> manipulator->setAllowThrow(false);
>
> view->setCameraManipulator(manipulator);
>
> ///////////////////////////////////////////////////
> // Set the viewer
> //////////////////////////////////////////////////
> viewer_->addView(view);
> viewer_->setThreadingModel(osgViewer::CompositeViewer::SingleThreaded);
> viewer_->realize();
>
> this->setFocusPolicy(Qt::StrongFocus);
> this->setMinimumSize(100, 100);
>
> this->setMouseTracking(true);
> }
>
>
>
>
>
> This method gets set once and shall set up the camera, interactor settings
> and the overall scene which only consists of one geode containing the
> geometry which shall be updated continiously.
> And after I have 'attached' the geometry, I am trying to update the
> geometry like this
>
>
> Code:
>
> void PointCloudViewOSG::processData(DepthDataSet depthData)
> {
> if (depthData.points()->empty())
> {
> return; // empty cloud, cannot do anything
> }
>
> const DepthDataSet::IndexPtr::element_type& index = *depthData.index();
> const size_t nPixel = depthData.points().get()->points.size();
>
> if (depthData.intensity().isValid() && !index.empty() )
> {
>     for (int i = 0; i < nPixel; i++)
>     {
>         float x = depthData.points().get()->points[i].x;
>         float y = depthData.points().get()->points[i].y;
>         float z = depthData.points().get()->points[i].z;
>         m_vertices->push_back(osg::Vec3(x
>             , y
>             , z));
>
>         // 32 bit integer variable containing the rgb (8 bit per channel)
> value
>         uint32_t rgb_val_;
>         memcpy(&rgb_val_, &(depthData.points().get()->points[i].rgb),
> sizeof(uint32_t));
>
>         uint32_t red, green, blue;
>         blue = rgb_val_ & 0x000000ff;
>
>         rgb_val_ = rgb_val_ >> 8;
>         green = rgb_val_ & 0x000000ff;
>
>         rgb_val_ = rgb_val_ >> 8;
>         red = rgb_val_ & 0x000000ff;
>
>         m_colors->push_back(
>             osg::Vec4f((float)red / 255.0f,
>             (float)green / 255.0f,
>                 (float)blue / 255.0f,
>                 1.0f)
>         );
>     }
>
>     m_geometry->setVertexArray(m_vertices.get());
>
>     m_geometry->setColorArray(m_colors.get());
>
>     m_geometry->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
>
>     m_geometry->addPrimitiveSet(new
> osg::DrawArrays(osg::PrimitiveSet::POINTS, 0, m_vertices->size()));
>     }
> }
>
>
>
>
> (Apperantly the code tag can somehow not handle the whitespaces but i will
> let it be since it is more readable than if everything is aligned)
>
> So my guess is that the  addPrimitiveSet(...)  shall not be called
> everytime I update the geometry, since it will push_back
> the primitive set everytime the geometry gets updated?
>
> Do I have to reattach my geometry after every update? Or do I have to
> rewrite my update method?
> So it boils down to the question  What steps are necessary to update my
> underlying geometry with new vertices and colors
>
> I have read the basic tutorials and looked for similar questions in this
> forum
> and the only thing that I could adapt is the use of VBO for performance
> gain
>
> PointCloudlibrary (PCL) is unfortunately not an alternative since of some
> incompatibilities with my application.
>
>
>
>
> Thank you!
>
> Cheers,
> Daniel
>
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=67011#67011
>
>
>
>
>
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>
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