Notes on spacing and angle

Two numbers decide most of what you see: how far apart the lines are, and how far one grating is turned from the other.

For parallel line gratings the width of the fringes is roughly the line spacing divided by the angle in radians. Two degrees on a 7 px spacing gives fringes around 200 px wide, which is a comfortable scale for a wallpaper. Halve the angle and the fringes double.

Concentric rings behave differently. Offset the centres and the fringes become a family of curves that bend around the midpoint, the way ripples from two stones in still water cross each other. Rings are more forgiving: almost any offset produces something pleasant.

Line thickness matters more than expected. Very thin lines give pale, airy fringes; heavier lines make the pattern feel dense and slightly mechanical. I usually try three thicknesses before I settle.

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