Double rotor

I decided some bands of rotating colour might do nicely for a poster background, open GIMP to do it, and discovered it wouldn't.

 

So I did it in RISC OS instead, using !Draw's Grade feature to interpolate lines of alternating rotated colour. Because !Draw can do more than this, I made the lines gently wavy to begin with. (Converted to a BMP bit map with !DrawToSpr.)

 

This gave me a circular do-dah with a fault in the middle (because you can't layer a sequence of lines so none are on top like impossible stairs). To get the size of the maximum inscribed circle, I rounded down the reciprocal root 2 of the radius, and took that as a centered canvas size reduction in PSP.

 

I got rid of the layers flaw with a second layer taken as a copy of the centre of the image, rotated 180° with it's flaw cut out, and recentred. Minimised the flaw first in MsPaint, temporarily replacing the centre colour with a contrasting one to make things stand out.

 

As I was repositioning the correction layer, using a difference filter, I noticed interesting interference patterns. So tried that again with multiply and a duplicate of the whole layer, and got much like what you see above. It just took clipping out the intersected area and a bit more resizing/clipping to get it as a standard screensize.

 

Each rotor consists of the same bézier curve, rotated so 16 complete a circle, and in alternate colours. 16 graduations between each of them were all that were necessary, and the lines are thick enough to overlap. This means that each of the two rotors consist of nothing more fancy than 256 wiggly lines.

 

This is my first really-cool looking wallpaper, and I expect to get paid a lot of money after sending it in the Lifehacker, dropped off in the foyer in a black refuse sack marked "thistles". Hang on a minute someone, just said they've disposed of the "toxic waste"...

 

 

Generated Friday 20th May 2011AD, 1538BST.

 

Done