How to Use this Applet
Viewing Different Objects
There are 3 different objects that can be viewed in order to
study the different camera and perspective transforms. Click on the
desired applet in the menu window to view these different
objects. These objects are all centered around the origin of the world
coordinate space.
Inputs to the Applet
The Inputs to the Applet are the Approximate Up Vector, the Look to
Position, the Look From Position(Camera Position), the Near Plane
Distance, the Far Plane Distance and the Screen Height. Any change in
these values will result in the images changing accordingly in the
World, View and Screen space.
Entering Values
The default values can be changed by two methods. One method is to
change the values directly in the textfield. The value is accepted
only when you hit the ENTER key. The textfield accepts only integer
values, both positive and negative.Another method is to increase or
decrease the values by 1 by clicking on the ">" and "<" buttons.
Rotating the Images
The images can rotated in the canvas by dragging the mouse in the
specific canvas. This can be done only in the
World Coordinate Space, View Coordinate Space and the Screen
Coordinate Space. By rotating the images, you can view the object from
all sides of the viewing frustrum. In the World Coordinate Space, the
X, Y and Z axes rotate along with the object and the frustrum and this
helps to understand the position of the object in the World
Space.
Viewing Frustrum
The Viewing Frustrum rotates with the object as the mouse is dragged
in the canvas. The Far Plane of the frustrum is colored blue, and the
Near Plane is colored Yellow. This color coding is consistent in the
World Coordinate Space, View Coordinate Space and the Screen
Coordinate Space. The UP vector is indicated by the Green Arrow.
Reset
Resetting the applet to bring back the default values can be achieved
by hitting the Reload button on the Netscape Navigator.
Degenerate Cases
If the UP vector and the Camera Position(Look From) vector are
collinear, then this will cause the image to degenerate. If the UP
vector along X, Y and Z axes is O then no image will be displayed in
the View Space and the Screen Space.
Image Display
The images are always displayed at the center of the canvas. All
translation and scaling of the images(both object and frustrum) are
dependent on the bounding box enclosing the frustrum and the object,
and also upon the width and height of the canvas.