本篇是创建游戏内核（5）【OO改良版】的续篇，关于该内核的细节说明请参阅创建游戏内核（6）。
接口：
class CAMERA
{
public:
CAMERA();
D3DXMATRIX* get_matrix();
void init();
void update();
void move(float x_pos, float y_pos, float z_pos);
void move_rel(float x_add, float y_add, float z_add);
void rotate(float x_rot, float y_rot, float z_rot);
void rotate_rel(float x_add, float y_add, float z_add);
void point(float x_eye, float y_eye, float z_eye,
float x_at, float y_at, float z_at);
void set_start_track();
void set_end_track();
void track(float time_ratio, float time_length);
float get_x_pos();
float get_y_pos();
float get_z_pos();
float get_x_rotation();
float get_y_rotation();
float get_z_rotation();
private:
float m_x_pos, m_y_pos, m_z_pos; // camera current position
float m_x_rot, m_y_rot, m_z_rot; // camera current rotation
float m_start_x_pos, m_start_y_pos, m_start_z_pos; // start tracking position
float m_start_x_rot, m_start_y_rot, m_start_z_rot; // start tracking rotation
float m_end_x_pos, m_end_y_pos, m_end_z_pos; // end tracking position
float m_end_x_rot, m_end_y_rot, m_end_z_rot; // end tracking rotation
D3DXMATRIX m_mat_world; // world transform matrix
D3DXMATRIX m_mat_translation; // translation matrix
D3DXMATRIX m_mat_rotation; // rotation matrix
};
typedef CAMERA* CAMERA_PTR;
实现：
//-------------------------------------------------------------------------
// Constructor, zero member data.
//-------------------------------------------------------------------------
CAMERA::CAMERA()
{
memset(this, 0, sizeof(*this));
}
//-------------------------------------------------------------------------
// initialize camera.
//-------------------------------------------------------------------------
void CAMERA::init()
{
update();
}
//-------------------------------------------------------------------------
// move camera to new position.
//-------------------------------------------------------------------------
void CAMERA::move(float x_pos, float y_pos, float z_pos)
{
m_x_pos = x_pos; m_y_pos = y_pos; m_z_pos = z_pos;
D3DXMatrixTranslation(&m_mat_translation, -x_pos, -y_pos, -z_pos);
}
//-------------------------------------------------------------------------
// move camera to new positoin which relative to current position.
//-------------------------------------------------------------------------
void CAMERA::move_rel(float x_add, float y_add, float z_add)
{
move(m_x_pos + x_add, m_y_pos + y_add, m_z_pos + z_add);
}
//-------------------------------------------------------------------------
// Build rotation matrix.
//-------------------------------------------------------------------------
void CAMERA::rotate(float x_rot, float y_rot, float z_rot)
{
D3DXMATRIX _mat_x_rot, _mat_y_rot, _mat_z_rot;
m_x_rot = x_rot; m_y_rot = y_rot; m_z_rot = z_rot;
D3DXMatrixRotationX(&_mat_x_rot, -x_rot);
D3DXMatrixRotationX(&_mat_y_rot, -y_rot);
D3DXMatrixRotationX(&_mat_z_rot, -z_rot);
m_mat_rotation = _mat_z_rot;
D3DXMatrixMultiply(&m_mat_rotation, &m_mat_rotation, &_mat_y_rot);
D3DXMatrixMultiply(&m_mat_rotation, &m_mat_rotation, &_mat_x_rot);
}
//-------------------------------------------------------------------------
// Build rotation matrix which relative to current rotation.
//-------------------------------------------------------------------------
void CAMERA::rotate_rel(float x_add, float y_add, float z_add)
{
rotate(m_x_rot + x_add, m_y_rot + y_add, m_z_rot + z_add);
}
//-------------------------------------------------------------------------
// move camera to new position and look at new target position.
//-------------------------------------------------------------------------
void CAMERA::point(float x_eye, float y_eye, float z_eye,
float x_at, float y_at, float z_at)
{
// Calculate angles between points
float _x_diff = x_at - x_eye;
float _y_diff = y_at - y_eye;
float _z_diff = z_at - z_eye;
float _x_rot = (float) atan2(-_y_diff, sqrt(_x_diff * _x_diff + _z_diff * _z_diff));
float _y_rot = (float) atan2(_x_diff, _z_diff);
// move camera to new position and look at new target
move(x_eye, y_eye, z_eye);
rotate(_x_rot, _y_rot, 0.0);
}
//-------------------------------------------------------------------------
// set camera's start tracking position and rotation.
//-------------------------------------------------------------------------
void CAMERA::set_start_track()
{
m_start_x_pos = m_x_pos; m_start_x_pos = m_y_pos; m_start_z_pos = m_z_pos;
m_start_x_rot = m_x_rot; m_start_y_rot = m_y_rot; m_start_z_rot = m_z_rot;
}
//-------------------------------------------------------------------------
// set camera's end tracking position and rotation.
//-------------------------------------------------------------------------
void CAMERA::set_end_track()
{
m_end_x_pos = m_x_pos; m_end_y_pos = m_y_pos; m_end_z_pos = m_z_pos;
m_end_x_rot = m_x_rot; m_end_y_rot = m_y_rot; m_end_z_rot = m_z_rot;
}
//-------------------------------------------------------------------------
// move camera to new position and ratation by giving time,
// 0 <= time_ratio <= 1.
//-------------------------------------------------------------------------
void CAMERA::track(float time_ratio, float time_length)
{
float time_offset = time_length * time_ratio;
float x = (m_end_x_pos - m_start_x_pos) / time_length * time_offset;
float y = (m_end_y_pos - m_start_x_pos) / time_length * time_offset;
float z = (m_end_z_pos - m_start_z_pos) / time_length * time_offset;
move(m_start_x_pos + x, m_start_x_pos + y, m_start_z_pos + z);
x = (m_end_x_rot - m_start_x_rot) / time_length * time_offset;
y = (m_end_y_rot - m_start_y_rot) / time_length * time_offset;
z = (m_end_z_rot - m_start_z_rot) / time_length * time_offset;
rotate(m_start_x_rot + x, m_start_y_rot + y, m_start_z_rot + z);
}
//-------------------------------------------------------------------------
// update new camera world transform matrix.
//-------------------------------------------------------------------------
void CAMERA::update()
{
D3DXMatrixMultiply(&m_mat_world, &m_mat_translation, &m_mat_rotation);
}
//-------------------------------------------------------------------------
// Get camera world transform matrix.
//-------------------------------------------------------------------------
D3DXMATRIX* CAMERA::get_matrix()
{
update();
return &m_mat_world;
}
//-------------------------------------------------------------------------
// Get camera current position (x coordinate).
//-------------------------------------------------------------------------
float CAMERA::get_x_pos()
{
return m_x_pos;
}
//-------------------------------------------------------------------------
// Get camera current position (y coordinate).
//-------------------------------------------------------------------------
float CAMERA::get_y_pos()
{
return m_y_pos;
}
//-------------------------------------------------------------------------
// Get camera current position (z coordinate).
//-------------------------------------------------------------------------
float CAMERA::get_z_pos()
{
return m_z_pos;
}
//-------------------------------------------------------------------------
// Get camera current rotation (x coordinate).
//-------------------------------------------------------------------------
float CAMERA::get_x_rotation()
{
return m_x_rot;
}
//-------------------------------------------------------------------------
// Get camera current rotation (y coordinate).
//-------------------------------------------------------------------------
float CAMERA::get_y_rotation()
{
return m_y_rot;
}
//-------------------------------------------------------------------------
// Get camera current rotation (z coordinate).
//-------------------------------------------------------------------------
float CAMERA::get_z_rotation()
{
return m_z_rot;
}