# Rotating a Point Around an Origin

• Jul 8th 2011, 01:46 AM
streaksy
Rotating a Point Around an Origin
Hello. I've been trying to find a guide to using matrices to rotate a point in 3D space around the origin. I can't find one that doesn't assume too much prior knowledge.

I have a point in space (X,Y,Z), and I want to find it's new position based on a rotation around a pivot - in this case the origin (0,0,0) - with a given 3D angle (pitch,yaw,roll).

To put it another way, I want to put something somewhere in a sphere, knowing it's position relative to the sphere's centre, spin the sphere on all 3 axies, and get the thing's new position relative to the sphere's centre.

I'm sure I have to make a 4x4 matrix, enter values in to its cells, and process it somehow, probably with another matrix. It's mostly the assumed knowledge of standard mathematical expressions that is holding me back, I think. I've spent the last few hours staring at matrix examples with their cells full of symbols and expressions that mean nothing to me. I need it explained to me in English with my only assumed knowledge being the variables involed, what a matrix is, sine&cosine of my XYZ angles. It's been done before when I was still in school in a way that worked for me.

I feel unworthy bothering relative geniuses with this, but I've read the rules and I really am trying. It's not that I don't want to learn or to have others solve all my problems - I'm just not getting it. I know how to use a search engine and this is the first time I've ever posted a mathematical problem in a forum or anywhere else. It's really stumped me. Obviously I don't understand much of mathematical notation, and I'm sorry about that. Hope it doesn't sound lazy, but I don't need to learn the minutae of the subject. I just need to solve this single problem and I'm done. I had this solved when I was a teenager. The problem is I can't find an explanation that isn't in terms above my understanding anymore. The processes they seem to describe don't even seem the same as when I solved it so I don't even know if I'm looking in the right places. I hope that explains my position... Thanks.
• Jul 8th 2011, 02:13 AM
streaksy
Re: Rotating a Point Around an Origin
It occurs to me that if I knew the distance and angle of the object from the origin then I could easily modify the angle and recalculate it's position. I can work out it's distance, but not angle. That involves dot products (I think) and that's just more stuff that's beyond me.
• Jul 8th 2011, 05:38 AM
streaksy
Re: Rotating a Point Around an Origin
i figured it out. THANKS FOR ALL YOUR AWESOME HELP AWESOME PEOPLE