Attributes and Behaviors of Primitives - Essentials of Interactive Computer Graphics - page 154

class UWB _ DrawHelper {

Source file.
uwbgl _ DrawHelper1.h/cpp
files in the Common Files/
DrawHelper subfolder of the
UWBGL _ D3D _ Lib4 project.

A: Functions to draw geometric primitives
virtual bool DrawPoint( vec3 position) { return false ;}
virtual bool DrawLine( vec3 start, vec3 end) { return false ;}
virtual bool DrawCircle( vec3 center, float radius) { return false ;}
.
B: Functions to set the attributes of the primitives
virtual void ResetAttributes();
virtual void SetShadeMode(eShadeMode mode); // Gouraud or Flat shading
virtual void SetFillMode(eFillMode mode);

// Wire frame or fill solid

UWB _ Color SetColor1(UWB _ Color color); // color to draw

D: Functions for supporting model transformations
virtual bool InitializeModelTransform();
.
private : ...
eShadeMode m _ ShadeMode; // enum data type for shading

m _ FillMode; eFillMode // enum data type of fill mode

UWB _ Color m _ Color1, m _ Color2; // storing the color setting

.

};

C: Implementation of attribute setting functions
void UWB _ DrawHelper::SetShadeMode(eShadeMode mode) { m _ ShadeMode = mode; }

void UWB _ DrawHelper::SetFillMode(eFillMode mode) { m _ FillMode = mode; }

.

Listing 7.1. The UWB _ DrawHelper class (Tutorial 7.1).

and circle. As we can see, in both cases, at label A, we obtain the reference
to the D3D RC. At labels B and C, we compute the vertex positions and per-
vertex attributes (e.g., color). At label E, we issue the drawing command. At
label D, we define the results of Gouraud shading, where for a line we define
linear interpolation between m _ Color1 from the starting vertex to m _ Color2 at
the ending vertex. Although for a circle, we define all the circumference vertices
to be m _ Color1 with the center of the circle being m _ Color2 ; this causes color
changing gradually from the center toward the circumference showing continuous
concentric circles with gradual color changes. The DrawPoint() function has a
similar structure and is not shown here.