How to use the ``camera''

The perspective projection is determined by the following parameters: the position of the camera (eyepoint), its direction (the vector from the eyepoint to the lookpoint), a vector that specifies the direction that is `up' in the projection plane (up-vector) and the focal length. The focal length controls the perpective in the same way a real camera does: Leaving the distance between eye and look-point stationary, a smaller focal length leads to a view, that shows more of the object at a higher grade of perspective distortion.

This menu's main part is a modified transformation menu (4.3.8).

 
Figure 4.18: Camera

FunctionRuler to choose the up-vector. As mentioned above the up-vector determines the ``up'' direction. In other words: Changing the up-vector is a kind of rotating the camera around the axis which is specified by look- and eyepoint; as a consequence the ruler controls the rotation angle.

Ruler to select the focal length. As said above, small focal length simulates a wide-angle lens; great focal length simulates a telephoto lens.

The Group below controls the position and rotation of the camera in space.

Ruler to scale the distance between eyepoint and lookpoint. Remember that in camera-rot the eye-point rotates around the lookpoint in the fix distance of 1.

The Group below controls the position of the look-point in space.

Reset the camera to default values. This means:
up-vector = (0,1,0),
lookpoint = (0,0,0),
eyepoint = (0,0,2),
distance = 2 and
focal = 2.

The view determined by these values is similar to the view without using the camera, except that there is perspective projection instead of orthogonal projection.