Creating Seamless Textures

The following is taken from an article posted to comp.graphics by {H}kan Andersson <zap@lysator.liu.se> on 8 September 1992, from Linkoping University, Sweden.

To obtain seamless textures, I think I know of three methods that comes to mind immediately.

The Mirror Trick

Simply mirror your original texture in X and Y. You will get something that repeats back and forth, but it is seamless. The problem is that this tiling is often visible, and that the seam may still be visible due to the sharp bend of for instance wood veins in the flip-seam.

HOWEVER: If you have an image manipulation package that allows you to 'stretch' around the images a bit, using the flipped images per above and then fooling around with the center (without messing with the edges) may give a decent-ish result.

Crossfading

Assume you have a square scanned piece of wood. Let's give it a 0,0 - 1,1 coordinate range.

For simplicity, let us only discuss the X coordinate case.

(Sadly, we only get a 0,5x0,5 piece of patternmatched wood out of a 1x1 piece of original wood if one uses this exact setup, but...)

At the left edge of the output image, do NOT place the left edge of the scanned wood! Instead the middle (X = 0.5 in input wood) are used, so we go from (left of output) = (0.5X of input) and (right of output) = (1.0 X of input). However, we cross-dissolve this with another image, who has (left of output = 0.0 X of input) and (right of output) = (0.5 X of input).

This gives us the exact 0.5 condition at the edges, with a smooth cross dissolve over the actual texture. Works quite OK for wood.

Do It By Hand

In your favourite paint program, do something like any or both of the above. I recommend using a variety of the second trick. The problem is often that you try (often in vain) to make the EDGES match. Stop that. Shift the image by half it's size in X and Y (assuming wraparound), thus making the EDGES THEMSELVES automagically matched. Then perform all fixing-up in the 'interior' of the image with stretching, overpainting, cut-n-paste, dissolving and all that jazz.

I myself use all three with increasingly good results going from the first idea listed here to the last. Of course, an increasing workload is imposed for each step down the list too :-)

The best result is the handmade one, even if the cross-dissolved can look good too. However, it can appear a bit blurrish in the 50%-50% regions, and they can sometimes show as "blurred crosses" on the surfaces.

Perhaps an ideal one would be the cross dissolve with some kind of triangulation morph of the image so one could assemble them to look good near the middle so the crossdissolve won't look blurred.