Let's start with a small 80x80 pixel grayscale image. Using the Checkerboard plug-in, create a checkerboard with 20x20 pixel squares.
Now, do at least a 3:1 zoom of the image so that you can precisely see what you will be doing. Using the rectangular selection tool, select the uppper-left group of four squares and apply *four times* a 90 degree Whirl. Yes, that's right, 4 times.
Why four times a 90 degree Whirl, and not just once a 360 degree one? Well, that's because the way interpolation works inside the Whirl plug-in. It is a simple bilinear interpolation. For such small images, it does not work very well for large whirls. So we better do several small whirls until we reach the desired result. Try it... just applying a 360 degree whirl one time will result in a much grainier image.
Now do the same for the upper-right four squares, but this time using a -90 degree whirl. This negative value is to turn the other squares in the opposite direction to the first group.
Now you can either do the same thing for the two lower groups of four squares (in the opposite whirl directions relative to the top groups), or use cut&paste.
To finish it off, select the upper-left and the lower-right groups and invert them. We now have a nifty and perfectly tileable pattern.
You can use this pattern for making more interesting things... bump maps, shadow masks, etc. Enjoy!
This page last updated: 1996/07/04 14:06:45