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# Working out delta theta to obtain a particular angle.

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2 replies to this topic

### #1MrMark  Members

Posted 05 June 2012 - 05:04 AM

Hi guys

I've been spending an embarrassing amount of time on a fairly simple problem. In my 2D world each entity has an orientation (theta) which represents the direction it is facing.

Given its current orientation and a target orientation, I want to find out:

The change in theta required to achieve the target orientation, rotating clockwise.
The change in theta required to acheive the target orientation, rotating counter clockwise.

the closest I got was abs(current - target) for clockwise rotations, and -abs(current - target), for counter clockwise rotations. But that falls apart when you go past 0.

This should be simple, but i can't seem to work it out.

### #2SiCrane  Moderators

Posted 05 June 2012 - 07:11 AM

If I understand your question, start with delta = target - current. If you want a clockwise rotation, and delta is negative add 360 degrees to delta. If you want a counterclockwise rotation and delta is positive subtract 360 degrees.

### #3MrMark  Members

Posted 05 June 2012 - 09:03 AM

If I understand your question, start with delta = target - current. If you want a clockwise rotation, and delta is negative add 360 degrees to delta. If you want a counterclockwise rotation and delta is positive subtract 360 degrees.

It works XD,