Questions about geode's setUpdateCallback

[zwt716]

I am a beginner in osg. I want to draw a rope, use a ball to draw the mass and a cylinder to draw the connection between the spheres. Update my vertexArray via geode->setUpdateCallback then redraw the rope on each update. But now the problem is that I can't update the shape of my rope. Below is my code.

class geodeCallback : public osg::NodeCallback
{
public:
	geodeCallback(osg::Vec3Array* vertexArray) : vertexArray_(vertexArray) {}
	virtual void operator()(osg::Node* node, osg::NodeVisitor* nv)
	{
		osg::Geode* geode = dynamic_cast<osg::Geode*>(node);
		if (geode)
		{
			vertexArray_->clear();
			for (int a = 0; a < ropeSimulation->numOfMasses - 1; ++a)
			{
				Mass* mass = ropeSimulation->getMass(a);
				osg::Vec3 pos = mass->pos;
				vertexArray_ ->push_back(pos);
			}
		}
		traverse(node, nv);
	}
private:
	osg::ref_ptr<osg::Vec3Array> vertexArray_;
};

osg::Geode* createRopeUseShapeDrawable()
{
	osg::Geode* geode = new osg::Geode;
	osg::Vec3Array* vertexArray = new osg::Vec3Array;

	for (int a = 0; a < ropeSimulation->numOfMasses; ++a)
	{
		Mass* mass1 = ropeSimulation->getMass(a);
		osg::Vec3* pos1 = &mass1->pos;
		vertexArray->push_back(osg::Vec3(pos1->x(), pos1->y(), pos1->z()));

	}
	for (int i = 0; i < vertexArray->size(); ++i)
	{
		osg::Vec3 pos = (*vertexArray)[i];
		osg::ref_ptr<osg::TessellationHints> hints = new osg::TessellationHints();
		osg::Geode* sphereGeode = new osg::Geode;
		hints->setDetailRatio(2.0f);
		osg::Vec3 oneShapepoint = pos;			
		osg::ref_ptr<osg::ShapeDrawable> oneShape = new osg::ShapeDrawable(new osg::Sphere(oneShapepoint, 0.01f), hints.get());
		oneShape->setColor(osg::Vec4(65.0 / 255, 105.0 / 255, 225.0 / 255, 1.0));			
		sphereGeode->addDrawable(oneShape);
		geode->addChild(sphereGeode);
	}
	for (int i = 0; i < vertexArray->size() - 1; ++i)
	{
		osg::Vec3 pos1 = (*vertexArray)[i];
		osg::Vec3 pos2 = (*vertexArray)[i+1];

		osg::ref_ptr<osg::MatrixTransform> mt = new osg::MatrixTransform();
		osg::ref_ptr<osg::ShapeDrawable> cylinder = new osg::ShapeDrawable();
		osg::ref_ptr<osg::TessellationHints> hints = new osg::TessellationHints();
		hints->setDetailRatio(2.0f);
		osg::Vec3 direction = pos2 - pos1;  
		osg::Vec3 cylCenter = (pos1 + pos2) / 2;		
		float height = (pos1 - pos2).length();		
		float radius = 0.01f;                  
		osg::ref_ptr<osg::Cylinder> cylinderPaint = new osg::Cylinder(osg::Vec3(0, 0, 0), radius, height);	
	       cylinder = new osg::ShapeDrawable(cylinderPaint, hints.get());
		cylinder->setColor(osg::Vec4(255.0 / 255, 228.0 / 255, 181.0 / 255, 1.0f));			
		osg::Geode* cylinderGeode = new osg::Geode;
		cylinderGeode->addDrawable(cylinder);

		osg::Matrix translationMatrix;
		translationMatrix.makeTranslate(cylCenter);
		osg::Matrix rotationMatrix;
		rotationMatrix.makeRotate(osg::PI_2, osg::Vec3(0, 1, 0));
		mt->setMatrix(rotationMatrix * translationMatrix);
		mt->addChild(cylinder.get());
		geode->addChild(mt.get());
	}
	osg::ref_ptr<geodeCallback> callback = new geodeCallback(vertexArray);
	geode->setUpdateCallback(callback);
	return geode;
}

[robertosfield]

If you are learning OpenSceneGraph might I suggest you just learn it's successor the VulkanSceneGraph instead. It's modern, better designed, far faster and properly support modern hardware.

The OpenSceneGraph is being maintained for legacy application, but for new applications development it's out of date as is OpenGL that it's built upon.

[nmielcarek]

I don't recall if this is needed for node callbacks, but you could try adding a geode->dirty(); or node->dirty(); call after updating the vertices so it informs the scene to regenerate them.

[xarray]

First, it is recommended to enable VBO on the geometry, and disable display-lists.
Call vertexArray_->dirty() if you change any element of the array.
Also, to ensure that the geometry has the correct bound, call geom->dirtyBound().
If you still use the default display-lists mode, you should also call geom->dirtyDisplayLists(), which is costly.