Things to Make and Do, part 5: anaglyphs (red-and-cyan 3D images)
January 31, 2010
I hope you have a pair of 3D glasses. If you do, then check this baby out:
(This is of course the same vertebra that we last saw in a multi-view composite figure at the end of the Brachiosaurus coracoid post.)
I’ve started to get into the habit recently of photographing some specimens from two slightly different angles: I couldn’t tell you exactly how much rotation I use, but I would guess it’s something like three to five degrees. That’s because I’ve found that flipping back and forth between the two images can give a useful sense of depth. If you don’t believe me, here are two not-quite-identical photos of the Archbishop’s Cervical S: open each of them in a tab, then flick back and forth between them:
It had occurred to me a while back that, just for fun, it would be interesting to composite them into a red-cyan 3D image. But I was prodded into action by two things. First, the free Lego marketing magazine that my boys get sent every month arrived, and with it a freebie pair of cheap cardboard red-cyan glasses. And second, Matt published a steropair of moon images on his blog. Matt’s friend Jarrod is a professional digital effects artist — in fact he’s won Emmies for stuff like blowing up Los Angeles for 24 — and threw together an anaglyph from the moon pictures. I got instructions from Jarrod on how to do this, and was gratified how easy it was. Here you go:
- Open the two photos as two layers of a single image.
- Using the Colour Levels dialogue, turn the red channel of one of the photos all the way down to zero (so that it appears in shades of cyan)
- Using the same dialogue, turn both the blue and green channels of the other photo down to zero (so that it appears in shades of red)
- Change the Layer Mode of the top layer to Brighten Only
That’s it, you’re done! Save the resulting composite image as a JPEG and upload it to your sauropod-vertebra blog. Jarrod uses PhotoShop; I use the Gimp, which is a free more-or-less equivalent program — the same technique works fine with both.
If I was pleasantly surprised at how simple the technique is, I was astounded at the quality of the result. I’d expected all the colour of the image to be gone, and to see a vague monochrome haze. Instead, I saw rock-solid 3D in full colour — truly informative images that convey the morphology of complex bones far better than any published figure I’ve ever seen. Seriously, go get your red-cyan glasses, you won’t regret it.
Here is another anaglyph of the same vertebra, in posterior view close-up, showing in detail what looks suspiciously like a hyposphene below and between the postzygs. (If this is indeed a hypophene, then I believe it’s unique among sauropods.)
Journals have occasionally published stereopair images of palaeo specimens: small images a couple of inches wide, next to each other, which you can supposedly see as a single 3D image if you cross your eyes in just the right light provided the wind is from the southeast — personally, I have never been able to see these things, thought Matt can. But these big, full-colour 3d images are orders of magnitude more information.
I’ve never seen one in a journal, in part of course because colour printing is such an insanely expensive luxury. But as Matt says, we all live in the future now, and I hope that’s about to change. I will be sending the Archbishop description, when it’s done, to PLoS ONE, which because of its electronic-only format can include any number of full-colour figures at no cost. I plan to send a few anaglyphs among the more conventional figures. Fingers crossed that they make it into the published version — I guess if I get a traditionalist reviewer, he might think these are frivolous and demand that I remove them. But they are not frivolous: they may be the most informative figures I have ever prepared.
Finally, I leave you with our old friend the pig skull, from all the way back in Things To Make And Do part 1 — but this time in glorious 3D!