How do I make a slide background spin from a central pivot point

[OLDBOSS]

I NEED TO MAKE A BACKGROUND IMAGE SPIN FROM A CENTRAL PIVOT POINT TO SIMULATE
A STAR PATTERN MOVING IN THE SKY. tHERE ARE NO OTHER ITEMS ON THE SLIDE.

 

[Bill Dilworth]

Hi Boss,

Couple of things...

1. Please take off the caps lock. It is considered to be shouting on the
internet.

2. You do not want the background to spin, you want a full frame image to
spin.

3. That spinning image must be large enough to fill the entire frame of the
slide, even when it is turned to any possible angle

4. To do this effect
a. Insert a starfield image (make sure Polaris is near the center)
b. Enlarge it so that it will cover the slide (no matter which angle is
being displayed)
c. Select the image
d. Add a Spin Emphasis animation
e. Adjust the time it should take to spin for your presentation
f. Make it start with previous, so that you don't have to click
anything

Additional instructions require knowing what version of PowerPoint you are
using and the file properties size of the slides

Bill Dilworth

 

[Bill Dilworth]

The math behind this is pretty straight forward geometry.

a = 1/2 of the slide height
b = 1/2 of the slide width

c = SQR( (a^2) + (b^2) )
... the longest distance from the center of the slide - special nod to
Pythagoras)

To get the ratio (%*100) of enlargement over a full slide image needed to
keep from showing the background of the slide, divide c by the smaller of a
or b.

If you are using a 7.5 by 10" slide (standard default), the answer is
166.66% enlargement OVER a full slide sized image. (or 12.5" by 16.65")

Bill