INTRO. Understanding the Photodex rotation system is very useful. It means you can choose a rotation direction much trial and error. Versions of ProShow prior to version 5 included the Rotate function. It represented rotation around the Z-Axis. This is an axis that is perpendicular to the plane of the screen and extends out of the screen toward the user and into the screen away from the user. With version 6 and later, ProShow included the feature called tilt. The program included vertical tilt and horizontal tilt. In vertical tilt, the layer rotates about the x-axis. In horizontal tilt, the layer rotates about the y-axis. These three rotation options provide a two-dimension (2D) program with a way to simulate a three-dimension (3D) environment.
3D Simulation. When it comes to determining the rotation direction about an axis, which direction is associated with positive or negative values (as represented in the associated rotation box for Horizontal Tilt, Vertical Tilt, or Rotate)? The answer is fairly simple but requires a little explanation. To start with, a rotation around an axis is
- Positive, if rotation is clockwise (to the right),
- Negative, if rotation is counterclockwise (to the left; also known as anti-clockwise)
- An easy way to remember it is with the Left Hand rule. If you curl your left hand’s fingers and point the thumb pointing toward your face, the fingers curl in a clockwise direction.
ROTATION DIRECTION. When it comes to determining the rotation direction about an axis, which direction is associated with positive or negative values (as represented in the associated rotation box for Tilt-Horizontal, Tilt-Vertical, or Rotate)? The answer is fairly simple but requires a little explanation. To start with, a rotation around an axis is
- Positive, if rotation is clockwise (to the right),
- Negative, if rotation is counterclockwise (to the left; also known as anti-clockwise)
An easy way to remember it is to use the Left Hand rule. If you curl the fingers of your left hand and point the thumb pointing toward your face, you will note that the fingers curl in a clockwise direction.
DETERMINING ROTATION DIRECTION
Refer to Figure 1, Rotation Coordinate System. All axes derive from a central point called the “origin.” All axes meet there. Let us assume that the thumb points along the axis in which you are interested. A positive axis direction for the
- X axis is LEFT,
- Y axis is UP, and
- Z axis is OUT of the screen (directly toward you)
So, a positive rotation direction occurs when the layer rotates in the direction of the curled fingers when the left thumb
- UP, rotates to the left (Tilt-Horizontal)
- LEFT, rotate is down (Vertical Tilt )
- OUT (from screen), rotate is to the right (Rotate)
TECHNICAL NOTE: Reference Figure 1. Normally, a positive axis is to the right for X, up for Y, and out for Z. The representation of these axes might be a little different depending on your application. However, the relative orientation between each axis will remain the same. Photodex experienced a little faux pax that wasn’t discovered until it was too late to change. That’s why the X axis is giving clockwise (positive) rotations on what would normally be a negative value axis. No big deal as long as things are consistent.
TILT ORDER CONSIDERATION:
Here’s another helpful hint when dealing with rotations. If you want to know a layer’s correct orientation for a given set of rotations, consider each rotation type in the following order:
- Tilt-Horizontal
- Tilt-Vertical
- Rotate
Or the following order:
- Rotate
- Tilt-Vertical
- Tilt-Horizontal
Never start out with Tilt-Vertical … it will throw you off every time!
That’s it!
Dale Fenimore
© 2012 Fenimore’s PhotoVideo Productions LLC
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