X3D is revised by Web3D Consortium combining its original VRML with the latest graphics technology. There are many kinds of encodings, including XML encoding. Different from other 3D technology (for example, Viewpoint, Cult3D, Shockwave3D, Virtools, Anark, etc.), X3D is an open standards file format. So it is not only suitable as a unified 3D data exchange format, but also can be used for real-time crossplatform network environment. The purpose of X3D is to set up a cross-platform method, used for transmitting the 3D scene in the internet network. Such a file format must describe the position of objects in 3D world and attributes such as color, material etc... No matter what operating platform user client is, so long as to implement the browser which accords with X3D standard on the platform. Then it is able to understand and display a 3D scene that X3D file describes. The applications of X3D are in various ways, such as visualization of engineering, Computer-Aided Design, visualization of medical science, teaching, simulation, multimedia, product demos, visual tourism, computer games. Because X3D adopts XML syntax, it can be further integrated with Web Services and distributed computing, and easy with future technology or applications.
http://www.aleeshainstitute.com/interior-designing-course.php
The scene graph is a kind of data structure which uses a tree to describe nodes in the X3D scene and their relation. For example, in Figure 1 the root node Root has two child nodes Transform A and Transform B. In addition, Transform A has a child node Shape A which has two child nodes Appearance A and Geometry A. In other words, Shape A is the parent node of Geometry A. And so on, there are many relations of parent node and child node between nodes in Transform B. Transform node represents the conversion of coordinate system, such as moving or rotating. The node will be affected by parent node usually. For example, the movement or rotation of Transform A will affect the position of Shape A in coordinate system, but not affect Shape C, because Transform A and Shape C have no relation of child and parent. Some nodes will not be affected by parent node, such as Time Sensor. If the Sensor node in Figure 1 is Time Sensor, it will not be affected by his parent node Transform B. If the child node will be affected by parent node, this kind of influence will be accumulated. For example, Shape C node will be affected by Transform B and Transform C at the same time.[4]
The scene graph is a data structure for application programmers. It offers functions of module loading and unloading the nodes for increasing work efficiency. As to X3D developer, it is a kind of node map. Before beginning to create the X3D content (especially to build and construct one complicated virtual world), there should be a scene graph in the brain. The developer had better take a piece of paper to draw out, not only can avoid using the repeated nodes for improving efficiency.
Scene Access Interface The greatest purpose of X3D is to describe a 3D virtual world and properties of object such as geometry, material, etc… It does not have the programmable ability, but some simple grammar only (Scripting Language) that is not enough to satisfy the applications of X3D. So VRML established Application Program Interface (API) outside JAVA called External Authoring Interface (EAI). At X3D, not only keeping the functions of EAI but also has proposed new Scene Access Interface (SAI) structure. Besides abstracting the original scene access service of EAI, SAI unified inside Scripting grammar and API which the outside program used. That is to say that offers the same access ability inside and outside, so can set up more strong and more reliable execution way. For this reason, X3D standard defined the language bindings of ECMAScript and JAVA[5]. See Figure 2(a), the API which inside Scripting grammar and outside program used is different in VRML. That is to say that accesses the node in VRML scene by way of different services. According to the specification of X3D, the used API of outside and inside has already been unified. All using the services defined in SAI to access the nodes in X3D scene.
