Attributes and Behaviors of Primitives - Essentials of Interactive Computer Graphics - page 163

class UWB _ Primitive {
public :
A: void Draw( eLevelOfDetail lod, UWB _ DrawHelper& draw _ helper ) const ;

B: virtual void Update( float elapsed _ seconds);

C: virtual void MouseDownVertex( int vertexID, float x, float y);
virtual void MoveTo( float x, float y);
D: void SetVelocity( vec3 velocity); // Set/Get velocity attribute
vec3 GetVelocity() const ;
bool IsStationary() const ;
.
protected :
E: vec3 m _ velocity; // instance variables for storing the attributes
UWB _ Color m _ FlatColor; // color for flat shading
float m _ PointSize; // If primitive is a point this is the size,

// otherwise, not used

virtual void SetupDrawAttributes(UWB _ DrawHelper& draw _ helper) const ;
virtual void DrawPrimitive( ... UWB _ DrawHelper& draw _ helper ) const =0;
.

F:

Source file.
uwbgl _ Primitive1.h/cpp
files in the Common Files/
Primitives

};

Listing 7.9. The UWB _ Primitive class (Tutorial 7.2).

subfolder of the

UWBGL _ D3D _ Lib5 project.

• B: The Update() function. The elapsed _ seconds parameter is the wall-
clock time since the previous invocation of this function. A subclass with
a time-varying internal state should override this function and update its
internal states accordingly.

• C: The mouse edit support functions. These functions are defined to
support abstract mouse interactions. For example, vertexID can be used
to represent the number of editing mouse clicks performed on behalf of a
primitive. We will examine how to use these functions to support general
editing of point, line, and circle primitives.

• D and E: The attributes and the corresponding set/get functions. All
primitive attributes are represented by instance variables in the Primitive
base class. As shown at label D1, attribute setting and getting functions
simply set/get the corresponding internal instance variables.