This week's book giveaway is in the Performance forum.We're giving away four copies of The Java Performance Companion and have Charlie Hunt, Monica Beckwith, Poonam Parhar, & Bengt Rutisson on-line!See this thread for details.
Win a copy of The Java Performance Companion this week in the Performance forum!

# How to calculate how many X/Y pixels to move object around a circle?

Max Simpson
Ranch Hand
Posts: 30
Hi,
When a user presses left or right, I would like to have an object move left or right around a circle (not rotating, but actually following the path of a circle). I need to figure out how many pixels on the X and Y axis to move on each step to move around a circle. Is their an easy way to calculate this? The radius of the circle is 50 pixels.
Thanks!

Layne Lund
Ranch Hand
Posts: 3061
One way would be to keep track of the angle that defines where the user is along the circle. From this angle and the radius of the circle, you can use some trigonometry and algebra to figure out the (x, y) coordinates.

HTH

Layne

Stan James
(instanceof Sidekick)
Ranch Hand
Posts: 8791
I did something in Pascal once to rotate an entire line drawing picture. To calculate the new position for each pixel I converted x,y coordinates to polar, added or subtracted some degrees, and converted back. There were some tricky cases for negatives as I recall. (I was a music major but my dad taught college math for 32 years and got me through some of it.) If you don't want to rotate your image you could use the same technique just to compute a new position for one corner of the image.