Step 1:
Create a new image of the desired size. Start with a random background by choosing Filter, Render, Clouds, Plasma, then click OK.



Step 2:
The contour comes from inherent quantization error in the gaussian blur algorithm. Start to generate this error by going to Filter, Blur, Gaussian Blur and choosing a blur of radius 110px horizontal and vertical.



Step 3:
For best results, at this stage you should switch to grayscale by choosing Colors, Desaturate, then checking the Lightness radio button and clicking OK. If you want a Moire-type pattern instead of a contour plot, do not perform the following blur. Otherwise, blur again by going to Filter, Repeat Gaussian Blur. Your result should be something like the following:



Step 4:
To find the quantization error and separate it from the smooth pattern, go to Filter, Edge Detect and choose the Edge... method. In the dialog box, choose Sobel edge detection using the smear mode, and turn up the amount to about 10. Apply the blur. Depending on the resolution of the image, you'll either have a contour plot or something that resembles a Moire pattern.



Step 5:
Now to bring out the pattern more vividly, we'll turn up the brightness and contrast. Go to Colors, Brightness and Contrast, and set Brightness and Contrast to your taste; I recommend Brightness at about 122 and Contrast around 119. If your lines are too close together, undo past the edge detection and Gaussian blur one or two times more.



Going Further:
From here, there's a lot of things you can do with this image. One of the simplest is coloring it with Colors, Colorize, turning up the Saturation, and selecting a proper Hue. You can also overlay a grid pattern to create an interesting tech-ish effect. Post up variations if you make them!

Very nice tutorial ^^,

At first I didn't really get the last part, but now I do ^^,

Interesting Output after playing with inverts and brightness and what not...


I used a black grid as you did, and put it over the image and the inverted it after I did a zoom motion blur. Then I played with the contrast and brightness ^^,

Final looks like:

Very cool! I'm glad you were able to put this to good use.

Just bumping this because it's kinda interesting and I'm planning on writing a few more tutorials soon.

woah, that's cool, how I wish I'd seen that before.

thanks for sharing here

Out of curiosity, why did you choose the contrast/brightness route instead of using the more fine-graind Curves tool?

In all honesty, because when I wrote this tutorial two and a half years ago, I was quite a bit vague on how the Levels tool actually worked.

Oh, levels are yucky too. Curves are sweet because you get a graph of the input color distribution, and you can change any corresponding point on the output distribution.

I am so glad that you have come up with a step by step guide on working this out. It has been some time since I have started wondering how to work more on the contour lines and its patterns! Anyway, up until a few minutes ago, I got stuck in step 4 where I had a hard time finding out the quantization error. Anyway, I just sorted out where I went wrong. I am now on the last part and will update more on how it went!

You sound like a bot, but on the off-chance that you're not, welcome to Cemetech.