Understanding memory management

In a typical programming scenario, the developer should create a pointer to the root node, which directly or indirectly manages all other child nodes of the scene graph. In that case, the application will traverse the scene graph and delete each node and its internal data carefully when they no longer need to be rendered. This process is tiresome and error-prone, debugging dozens of bad trees and wild pointers, because developers can never know how many other objects still keep a pointer to the one being deleted. However without writing the management code, data segments occupied by all scene nodes will never be deleted, which will lead to unexpected memory leaks.

This is why memory management is important in OSG programming. A basic concept of memory management always involves two topics:

Some modern languages, such as C#, Java, and Visual Basic, use a garbage collector to free memory blocks that are unreachable from any program variables. That means to store the number of objects reaching a memory block, and deallocate the memory when the number decrements to zero.

The standard C++ approach does not work in such a way, but we can mimic it by means of a smart pointer, which is defined as an object that acts like a pointer, but is much smarter in the management of memory. For example, the boost library provides the boost::shared_ptr<> class template to store pointers in order to dynamically allocated related objects.