3D Graphics Using OpenGL ES 2.0 - Beginning Android 3D Game Development - page 106

The Camera class's constructor is shown in Listing 4-21. The constructor initializes the camera with
the input parameters and performs the following functions:

m_Orientation .
Sets the camera projection frustrum using the user specified input parameters

 Creates a new Orientation class object called



Projleft , Projright , Projbottom , Projtop , Projnear , and Projfar .
Sets the camera's local coordinate axis and position. Sets the forward local axis



(z axis), up local axis (y axis), and the right local axis (x axis). The right local axis
is calculated from the cross product of the Center and Up vectors.

Listing 4-21. The Camera Class's Constructor

Camera(Context context,
Vector3 Eye, Vector3 Center, Vector3 Up,
float Projleft, float Projright,
float Projbottom, float Projtop,
float Projnear, float Projfar)
{
m_Orientation = new Orientation(context);

// Set Camera Projection
SetCameraProjection(Projleft, Projright, Projbottom, Projtop, Projnear, Projfar);

// Set Orientation
m_Orientation.GetForward().Set(Center.x, Center.y, Center.z);
m_Orientation.GetUp().Set(Up.x, Up.y, Up.z);
m_Orientation.GetPosition().Set(Eye.x, Eye.y, Eye.z);
// Calculate Right Local Vector
Vector3 CameraRight = Vector3.CrossProduct(Center, Up);
CameraRight.Normalize();
m_Orientation.SetRight(CameraRight);
}

The SetCameraProjection() function actually sets the projection matrix, using the Matrix.
frustumM() function to generate the matrix, and puts it in m_ProjectionMatrix (see Listing 4-22).

Listing 4-22. Setting the Camera Frustrum

void SetCameraProjection(float Projleft,
float Projright,
float Projbottom,
float Projtop,
float Projnear,
float Projfar)
{
m_Projleft = Projleft;
m_Projright = Projright;
m_Projbottom = Projbottom;
m_Projtop = Projtop;
m_Projnear = Projnear;