Environment
This tutorial was conducted in a command line environment consisting of Unix and Linux machines. Command line means that what you want the computer to do is input as text (commands), as opposed to a graphical user interface where you can click on an icon and a program will be executed.
3D Basics
- We need a way to specify location in a virtual 3 dimension world
- Use a set of co-ordinate axis
- Y-axis (blue arrow) specifies up and down
- X-axis (green arrow) specifies left and right
- Z-axis (red arrow) specifies in front and behind
- The computer screen we use is 2 dimensional, how do we move in 3 dimensions?
- 3 button mouse:
- Left button we can translate in X and Y
- Middle button we can zoom in Z (moves things closer or farther)
- We can rotate object with right button using a trackball interface.
The Circle indicates outline of a virtual sphere.
- When we drag the mouse from one side of the circle to the other,
it is as if we are rotating the sphere 180 degrees. (Imagine
putting the mouse on a point on the sphere and then dragging
the sphere along with the mouse). We can rotate the object
in almost all directions this way.
- Moving the mouse around the outside of the circle let us rotate
around the eye point (imagine a line from your eye to the
middle of the screen).
- When we drag the mouse from one side of the circle to the other,
it is as if we are rotating the sphere 180 degrees. (Imagine
putting the mouse on a point on the sphere and then dragging
the sphere along with the mouse). We can rotate the object
in almost all directions this way.
- Left button we can translate in X and Y
- With this interface, we can move around pretending we are in 3 dimensions on a 2 dimensional screen. This is just one of many methods of moving around in 3D.