Coordinate Systems - Essentials of Interactive Computer Graphics - page 262

We remind ourselves that Equation (10.15), or the M w 2 d operator, is the net trans-
formation that would be applied to vertices specified in WC space. From Equa-
tion (10.11), we observe that, as programmers, we are only responsible for M w 2 n ,
or half of the M w 2 d operator. The other half of the operator, M n 2 d , is computed
automatically by the graphics API. In this case, we analyze Equation (10.15) and
the M w 2 d operator to understand the details of the images generated in the UI
drawing device. We will examine the effects of changing the WC window based
on tutorial implementations. Let us first extend our library to support working
with the WC window.

UWBGL_D3D_Lib10

Change summary. See p. 522
for a summary of changes to
the library.

This library extends from Lib9 by extending the UWB _ WindowHandler class to
support the definition of the WC window and programming of the M w 2 n operator.
Recall that the WindowHandler object is defined to abstract a view/controller
pair. For the WindowHandler object to properly display different regions of the

class UWB _ WindowHandler : public UWB _ IWindowHandler {
.

Source file.
uwbgl _ WindowHandler3.h
file in the Common Files/
WindowHandler

// Set/Get methods for accessing the m _ WCWindow object
A: virtual void SetWCWindow( const UWB _ BoundingBox &window);
virtual const UWB _ BoundingBox * GetWCWindow();
// Set/Get methods for the drawing device (via m _ hAttachedWindow)
B: virtual void SetDeviceSize( int width, int height);
virtual void GetDeviceSize( int &width, int &height);
// wcPt -> dcPt (Equation 10.13 )
C: virtual void WorldToDevice( float wcX wcY, int &dcX &dcY);
// dcPt -> wcPt (Equation 10.19 )
virtual void DeviceToWorld( int dcX dcY, float &wcX &wcY);
// Drawing the WCWindow
D: virtual void DrawWCWindow(UWB _ DrawHelper&);
// Compute M w 2 n and load to API matrix processor
E: virtual void LoadW2NDCXform() = 0;
protected :
.
HWND m _ hAttachedWindow; // The UI drawing device (a MFC Window)
F: UWB _ BoundingBox m _ WCWindow; // Window for the World Coordinate
};

subfolder

UWBGL _ D3D _ Lib10

of the

project.

Listing 10.7. The WindowHandler class of UWBGL _ D3D _ Lib10 .