Introduction¶

Scenegraph is perhaps the most fundamental concept in MAGES SDK. It is this root module that powers and distinguishes ORamaVR’s educational platform from the herd.

In this section, we proceed to present Scenegraph’s architecture and how it structures all development.

The image above shows the transformation of a structured storyline into the MAGES scenegraph tree.

Scenegraph Explained¶

In order to achieve a goal whether it is the restoration of a statue or a medical operation you need to follow a list of tasks/steps in a sequential order. We are referring to those steps as Actions.

For instance, if we want to hang a painting on the wall we have to perform the following steps (Actions):

Mark the wall using a pen.
Hammer a nail at the marked spot.
Hang the painting on the wall.

Those are three steps that someone needs to complete to hang a painting on the wall. Having those steps in mind we create nodes, each one representing an Action.

However in more complex applications there are dozens of Actions, in this case a sequential representation is not very convenient. For this reason we implemented the Scenegraph architecture.

A Scenegraph is a tree with three levels of depth. The root of the tree defines the operation/process, on depth 1 we have the Lesson nodes, depth 2 the Stage nodes and finally depth 3 the Action nodes.

The procedure runs only on Action nodes but we also use the other nodes in a tree format to merge parts of the simulating procedure.

For instance, we can present the above 3 Actions in a tree format as follows:

In this scenario we decided to group the first two Actions in a Stage since both of them are referring to steps that are linked with the nail. The last action can be placed alone in a stage particularly for this case.

After those optimizations, this lesson can be used in a more complex procedure with other lessons to construct a bigger Scenegraph tree. However, pay attention that even though we have multiple types of nodes (Lesson, Stage, Actions), only the Action nodes have customizable behavior.

Note

The operation runs only on Actions, the other nodes are for traversal and scene management.

Scenegraph is implemented under the “Scene Graph” actor in the Unreal level. This actor will contain the Lesson, Stages and Actions. Scenegraph will manage, perform and run all the Actions as an educational pipeline.

The Scenegraph xml file¶

The Scenegraph structure is saved in an .xml file An example of this xml file can be seen in Sample App (SampleApp.xml).

As you can see in this snippet we generate the Knossos Lesson which has one Stage and two Actions. The format of this xml needs to be as this example indicates, otherwise there will be errors in importing.

Below there is an explanation of the xml tags used in this script.

ArrayOfLessons	Contalls all the Lessons.
Lessons	Contains a Lesson.
Lesson_Name	Name of Lesson. This string will be used to timeline UI as it will be shown to the UI button in Lesson Timeline.
Stages	Contains a Stage.
Stage_Name	Name of Stage. This string is only used to name the gameobject and nowhere else.
Actions	Contains all Actions.
Action	Name of Action. This string needs to address in a small sentence the purpose of current Action. This string will appear on the gamification monitor (as the current Action) so in a few word needs to address the current Action (e.g. Remove the Flashing Minoan Jar).
ActionClassName	Contains the Class name of this Action. Each Action has an Action script that needs to be added to the Action’s gameobject Node. This script will automatically run by Scenegraph when the right time comes. In order to have a clear project we recommend to store all the Action scripts under the format LessonX/StageX/ActionX to match the Scenegraph Nodes.
ActionType	Defines the difficulty of Action. This variable is used for analytics.
AverageActionTime	Average completion time of Action. Again see analytics for further information.
IsDemoApplicable	Define if the Action will be part of the Demo. You can create a demo version of your product by selecting which actions will be included. The other actions that will remain out of the demo will just perform when reached during the gameplay. Set y (for yes), n (for no) and l (for last action of demo). After the last Action of demo Scenegraph will put the operation end Action automatically to finish the Demo.