Previous: Our first scene Main Index Next: Add an object


Understanding Modlight Coordinate System

The usual coordinate system for Modlight has the positive y-axis pointing up, the positive x-axis pointing to the right, and the positive z-axis pointing outside the screen as follows:

The right-handed coordinate system (the z-axis is pointing through the user)

This kind of coordinate system is called a right-handed coordinate system. If we use our right-hand's finger we can easily see why it is called right-handed. We just point our thumb in the direction of the positive x-axis (to the right), the index finger in the finger in the direction of the positive y-axis (straight up) and the middle finger in the positive z-axis direction (backward). We can only do this with our left hand. If we had used our left hand we would not have been able to point the middle finger in the correct direction.

The right hand can also be used to determine rotation directions. To do this we must perform the famous "Computer Graphics Aerobics" exercise. We hold up our right hand and point our thumb in the positive direction of the axis of rotation. Our fingers will curl in the positive direction of rotation. Similarly if we point our thumb in the negative direction of the axis our fingers xill curl in the negative direction of rotation.


Previous: Our first scene Main Index Next: Add an object