the hatch pattern on the drawing I'm working on is kicking out a right moiré effect.

http://en.wikipedia.org/wiki/Moir%C3%A9_pattern

So... tel me... what's your favourite optical illusion?

Mine is the Same Collour Illusion. Except I kinda hate it with a passion at the same time, cos I just can't force my eyes to see past it.

http://en.wikipedia.org/wiki/Same_color_illusion