Working with the Camera - Essentials of Interactive Computer Graphics - page 414

upwards movement
of camera
results in downwards shift
in image

Current
Camera Position

downwards movement
of camera
results in upwards shift
in image

Figure 15.9.

Vertical tracking displacement directions.

void UWB _ Camera::MouseTrack( int x, int y)
// compute dx/dy using mouse x/y movements
A: float dx=... dy=...
// comptue eye axis frame: V v
B: view _ direction = m _ LookAt - m _ CameraPos;
cross _ direction = cross(up _ direction,view _ direction); // V w
normalize(cross _ direction); // V w
up _ direction = cross(view _ direction,cross _ direction); // V u
normalize(up _ direction);

V u

//

// V δ =( − dx × V w )+( dy × V u )
C: delta = (-dx * cross _ direction) + (dy * up _ direction);
m _ CameraPos = m _ CameraPos - delta; // p e = p e − V δ
m _ LookAt = m _ LookAt - delta; // p a = p a − V δ

.

Source file.
uwbgl _ Camera _ Xform1.cpp
file in the Common Files/

Listing 15.14. The UWB _ Camera support for tracking.

Camera subfolder of the

UWBGL _ D3D _ Lib14 project.

15.3.3 Dolly: Zooming the Camera

From real-world experience, we know that the view distance v d determines the
size of the object on the eventual photograph. When we want to take a closer
examination of an object, or zoom in on an object, we move the camera closer