Webpage background weirdness - ? Explanations Welcome!

July 18, 2010 6:48 PM

Explanation for website background behaviour please? Why & how does this websites' background do what it does, namely travel the opposite way to the main body of the page when scrolling with a mouse wheel?

Replicable in both FF and Google, but not in IE...

If it is code could someone specify what and where as I can't see it :)

I've contacted the site owner and he never noticed it before (!) and is at a loss to explain it. The actual wallpaper makes it even weirder - almost optical illusion-ish.

posted by DrtyBlvd to Computers & Internet (7 answers total)

Best answer: It's just a clever (or accidental) result of the tiling. If the height of the pattern is n pixels, your browser scrolls n-x pixels, and so the image SEEMS to scroll down by x pixels.

Sorry if that doesn't make much sense, it's the only way i can think of to explain it.
posted by frwagon at 6:49 PM on July 18, 2010

frwagon's got it - it's similar to the optical illusion where a fast-spinning hubcap will seem to spin quickly, slow down and pause, then start spinning in the opposite direction. (This also works with ceiling fans.)

Basically, since each section looks just like the others, you see a section moving in one direction, but really you're seeing the adjacent section in a closer position. Ugh, yeah, also no the best way to explain it, but hopefully if enough of us pile in here we'll be able to explain it properly.
posted by Zephyrial at 6:54 PM on July 18, 2010

As others have said, it's an optical illusion. It only looks like it's moving backwards. If you slowly drag the scrollbar down, rather than using the mouse wheel, you'll see that it's not actually moving backwards.
posted by MexicanYenta at 7:10 PM on July 18, 2010

It's an optical illusion. If you alter your mouse settings to scroll a different number of lines per "click" the behavior changes. I changed mine from 3 lines to 4 and the effect disappeared. (In Windows: Control Panel >> Mouse >> Wheel >> Roll the Wheel One Notch to Scroll the Following Number of Lines)

Most likely the owner of the site never noticed it because his mouse wheel settings are such that the effect doesn't occur for him.

On preview, "ditto".
posted by ElDiabloConQueso at 7:14 PM on July 18, 2010

Best answer: Also, here's the effect Zephyrial referred to above:

http://en.wikipedia.org/wiki/Wagon-wheel_effect
posted by ElDiabloConQueso at 7:16 PM on July 18, 2010

And if you drag the bar down instead of scrolling you'll see how it slides up instead of skipping down.
posted by msbutah at 7:46 PM on July 18, 2010

It only does it if I page down. if i use the mouse wheel its pretty obviously mopvign with the text
posted by mary8nne at 3:33 AM on July 19, 2010