Attributes and Behaviors of Primitives - Essentials of Interactive Computer Graphics - page 157

class UWB _ PointGeometry {
.
// sets m _ point instance variable

A: void SetLocation( float x, float y, float z=0.0f);

.
// sets m _ color instance variable

void SetColor( const UWB _ Color& color);
.

B:

void Draw(UWB _ DrawHelper * pDrawHelper) const ;
.

C:

Source file.
uwbgl _ PointGeom1.h/cpp
files in the Common Files/-
Geoms

protected :
.
vec3 m _ point;

subfolder of the

UWBGL _ D3D _ Lib4 project.

// to store the location of the point

UWB _ Color m _ color; // color attribute of the point

.

void UWB _ PointGeometry::Draw(UWB _ DrawHelper * pDrawHelper) const {
.
pDrawHelper->ResetAttributes();
pDrawHelper->SetColor1(m _ color);
pDrawHelper->SetPointSize(m _ point _ size);
pDrawHelper->DrawPoint(m _ point);

}

Listing 7.4. The UWB _ PointGeometry class (Tutorial 7.1).

Point/line/circle geometries. When a geometric primitive has access to the
DrawHelper class, it can draw itself to the API-specific device by calling the
appropriate attribute-setting and primitive-drawing functions. For example, List-
ing 7.4 shows an API-independent PointGeometry class, where this class does
not contain any graphics API-specific function calls. We see that in this case,
the point class has a simple public behavior where we can set its geometry (A)
and attribute (B). The Draw() function simply delegates the responsibilities to
the DrawHelper class. If the pDrawHelper pointer references a D3DDrawHelper
class (as shown in Listing 7.2), then the corresponding D3D drawing would occur.