The Rambling Chronicles: Notes » C++ http://notes.theramblingchronicles.co.uk Making sense is optional Thu, 26 Aug 2010 10:09:56 +0000 en hourly 1 http://wordpress.org/?v=3.0.1 C++ Matrix Rotation http://notes.theramblingchronicles.co.uk/2008/03/04/geometric-matrix-rotation/ http://notes.theramblingchronicles.co.uk/2008/03/04/geometric-matrix-rotation/#comments Tue, 04 Mar 2008 22:21:05 +0000 Tom http://www.tflash.co.uk/posts/20 Maths Alert!

A bit of background is needed on this one: I was attempting to take a bunch of coordinates and rotate them around a circle on the z axis. Simple. No, it’s not when you know how to do the maths (matrix based rotations) on paper, but you have no idea how to apply the maths knowledge to a programmatic solution. After lots of searches of functions that looked extremely complicated and feature rich (I wanted simple, one function code), I finally discovered the answer:

x1 = cos(angle)*x - sin(angle)*y;
y1 = sin(angle)*x + cos(angle)*y;

What this basically does it take your two points, x and y, and rotate them by the amount given as angle, storing the new values in x1 and y1. You need to have x and y to begin with, as it needs something to rotate.

]]> http://notes.theramblingchronicles.co.uk/2008/03/04/geometric-matrix-rotation/feed/ 0 C++ cout http://notes.theramblingchronicles.co.uk/2008/01/30/c-cout/ http://notes.theramblingchronicles.co.uk/2008/01/30/c-cout/#comments Wed, 30 Jan 2008 15:21:14 +0000 Tom http://www.tflash.co.uk/posts/15 Useful tip for C++ programmers who’ve come from a different language like Python, Java etc.
Use cout << "some text" << aVariable; instead of trying to concatenate (join) the strings like you would in PHP, Python, Java etc. Trying to join the variable (if it’s not already a string) to a string is overly complex if your aim is just to write out the result of a calculation or something for debugging.

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