HOW TO USE OFFSET TOOL IN PHOTOSHOP
This is to show my surface pattern designer friends how to use the offset filter to create seamlessly repeating tiles, in Photoshop - I'm using CS6 and a Wacom Intuos Pro, neither of which are essential for this exercise. I don't claim to be an expert at this in any way - it just tries to fill a gap where there aren't enough comprehensive instructions online or in books.
3 things to remember:
1) your document should be created with an even number of pixels, width and height, because when we go to use the offset filter we need to divide exactly in half. In this video the document is 3000 x 3000 pixels so for the offset tool I divide in half to get 1500. (Your document doesn't have to be square though) .
2) Don't have any stray pixels off the canvas on the layer you are going to offset. Use the crop tool to be on the safe side.
3) the offset tool only works on one layer at a time so take this into account when arranging your motifs.
If anyone uses any different methods, do share!