The file intro_main.c++ contains the nodes of the application tree that determine the opening screen. Figure 2 shows the layout of nodes. A light node is added to shine directly onto the map of china. The map of china is a texture node assigned to a square SoFaceSet node.
The common properties of the selectable text is attached to the tree next. The font type is set, the material and binding is set with appropriate nodes. See the source code for exact settings of properties. Four selectable SoText3 type text objects are created and attached to the tree.
As an example the selectable text subtree for Hainan Island is shown in Figure 2. Each selectable text subtree starts with a SoSelection node and a callback function that changes the SoSwitch whichChild property of the top level switch when that text is selected. Under the SoSelection node is a transform that positions the text on the map, a SoProfileCoordinate and SoLinearProfile nodes that define the text properties and finally the SoText3 node itself.
The other three nodes are identical to the Hainan Island node except for changing the text values and text position.