Hierarchical Modeling - Essentials of Interactive Computer Graphics - page 296

class CPrimitiveControl : public CDialog {
// ... details related to MFC not shown ...
A: void SetPrimitive(UWB _ Primitive * p); // Sets the m _ Primitive pointer at label B

protected :
B: UWB _ Primitive * m _ Primitive; // GUI event service functions would change
// the attributes referenced by this pointer
// ... GUI event service functions not shown ... Source file.

PrimitiveControl.h file
in the Controls folder of the
D3D _ SceneTreeControl
project.

};

Listing 11.10. The CPrimitiveControl class of Tutorial 11.5.

Control . During the CSceneTreeControl construction, in the OnInitDialog()
function at label C, the BuildSceneTree() function is called with the root node
of the model (the arm). This function builds the tree structure on the left of
the SceneTreeControl (see Figure 11.10 ) . At label D, the ReplaceDialog
Control() functions are called to place the XformInfoControl and Primitive
Control into their respective placeholders in the SceneTreeControl .
The implementation of CXformInfoControl wasdiscussedinTutorial9.7
(p. 251). CPrimitiveControl is similar to CXFormInfoControl where an ap-
propriate GUI element is defined for each controllable attribute in a UWB _
Primitive class. As illustrated in Listing 11.10, the user of the CPrimitive
Control class calls the SetPrimitive() function (label A) to set the m _ Primi
tive pointer (label B). The GUI elements in the PrimitiveControl container
set the attributes of the primitive referenced by the m _ Primitive pointer.
The CSceneTreeControl class will be reused in tutorials throughout the rest
of this topic.

11.3 Scene Trees and Scene Graphs

In general, a hierarchical model is a geometric model built based on generations of
transformation operators and primitives, where the user has independent control
over components in the model. In our case, with the functionality defined in the
SceneNode class, a hierarchical model is simply a scene node hierarchy.
In the previous section, we introduced and worked with the SceneNode class
to abstract and become familiar with the functionality of a scene node. In this
section, we concentrate on the hierarchy that interconnects scene nodes. We will
see that the scene tree, a straightforward tree hierarchy of scene nodes, can easily
be constructed and maintained to model objects with independently controllable