Attributes and Behaviors of Primitives - Essentials of Interactive Computer Graphics - page 178

• Approach. To introduce the PrimitiveList class, a Primitive subclass
that has a collection of Primitive references; examine how to work with
this class.

Figure 7.12 is a screenshot of running Tutorial 7.4. This tutorial extends Tuto-
rial 7.3 by supporting the creation of any number of point, line, and circle primi-
tives with motion and by supporting the collision between these primitives.

Figure 7.12.

Tutorial

7.4.

UWBGL_D3D_Lib7

Change summary. See p. 517
for a summary of changes to
the library.

When we examine the supporting library for this tutorial, we see that only two
files are added to the Common Files/Primitives subfolder: uwbgl _ Primitive
List.h/cpp . These two files implement the UWB _ PrimitiveList class. List-
ing 7.21 shows that UWB _ PrimitiveList is a subclass of the Primitive class.
At label D, we notice that this class has an array of references to Primitive .
With the corresponding interface methods at label B, this class can behave just
like a linked list of Primitive pointers. The functions defined at label A ensure
the update of all primitives in the list when appropriate and proper support of col-
lision functionality. The overrides at label C ensure that all primitives in this list
can be drawn when the Primitive::Draw() function is called.

class UWB _ PrimitiveList : public UWB _ Primitive {
A:

virtual void Update( float elapsed _ seconds);
virtual const UWB _ BoundingVolume * GetBoundingVolume( eLevelOfDetail lod ) const ;
void DrawChildBoundingVolumes(... UWB _ DrawHelper * , UWB _ Color color) const ;

B:

int Count() const ;
UWB _ Primitive * PrimitiveAt( int index);

Source file.
uwbgl _ PrimitiveList1.h
file in the Common Files/
Primitives

void Append(UWB _ Primitive * pPrimitive);
void DeletePrimitiveAt( int index);
protected :
.

subfolder of the

UWBGL _ D3D _ Lib7 project.

virtual void DrawPrimitive( eLevelOfDetail lod, UWB _ DrawHelper& draw _ helper ) const ;
virtual void SetupDrawAttributes(UWB _ DrawHelper& draw _ helper) const ;

C:

UWB _ PointerArray<UWB _ Primitive * >m _ list;
UWB _ BoundingBox m _ bounds;

D:

// union of all primitive bounds

};

Listing 7.21. The UWB _ PrimitiveList class (Tutorial 7.4).