2007 ASRA Earth & Space Science Module

How to Take 3D Stereo Photos

A normal photo only shows the scene from one angle, which of course gives a flat image. When you're really there, you see with two eyes, in "stereo". Surprisingly, it's pretty easy to take two images, and see them in 3D.
You can take 3D stereo pictures with any camera:

Hold the camera level, and take a picture. This is the view from the left eye.
Move to the right a few inches and take another picture, facing the same direction as the first one.

The further you move the camera, the more of a 3D effect you'll see, but too far apart and your brain can't fuse the images--just like looking crosseyed at the tip of your nose. For extreme closeup images, like flowers, you should move the camera only a centimeter or so between shots. For really far away stuff, like mountains, you can actually move the camera by dozens of meters! Check out some of our stereo pairs to see what they look like.

For objects that move, like people, the separate pictures from the left and right eye positions aren't quite at the same time, and so the two images won't line up. But it's fairly easy to build a little mirror rig to simultaniously take the left and right eye images--here's a little mirror camera rig I built, and some photos from it.

allview fadeout levitate roboparsons

How to View Stereo Photos in 3D

You can then build red-green "anaglyphs" using an image editor program like Photoshop (the GIMP should work too, but at least in version 2.2, it doesn't seem to!). Here's how:
1. Open the left eye picture. Copy the whole picture (Select -> All. Edit -> Copy.)
2. Open the right eye picture. Switch the "Channels" box so you're only editing the Red channel--you want Red highlighted, but nothing else highlighted (click "Channels", next to the "Layers" box, then click the label "Red"). Paste the left eye picture into the red channel (Edit -> Paste).
3. Now the red channel has the left eye picture, and the green and blue channels have the right eye picture.
4. Put on a pair of red-green "3D glasses", and look into the picture! You may have to shift around the red channel to make it line up with the green and blue (you can use the four-way-arrow move tool for this).
- Here are some of our anaglyphs:
  
  3dbear barbedwire_analyph office_L roots_stereo ruins_stereo
With practice, you can actually see stereo pairs in 3D without glasses. I do this all the time. Some people prefer the crosseye technique instead, but I get less dizzy with the walleye.
You can also buy a set of LCD shutterglasses (like this $40 pair from eDimensional), that latch onto your VGA CRT monitor's vertical sync line. The glasses can black out each eye independently, and with the right drivers (which are tricky to set up!), your monitor flashes the proper image to each eye, and you see in stereo! This sorta-kinda works with some DLP projectors (sometimes it works perfectly, but the eyes are flipped and the glasses need to be flipped upside down! Sadly, folks with DVI or LCD monitors can't use stereo glasses.
Like we did, you can go to the ARSC Discovery Lab, deep inside UAF's library, to see an awesome headtracking active stereo setup.

Other Fun Photo Stuff

Mount a camera on top of a long pole. This gets you above most of the annoying shrubs, trees, and signs that clutter up most photos. PVC pipe is long, cheap, and works well, but it is pretty floppy! The trickiest part is pushing the shutter on top of the long pole--I've tried the following ways to push the camera shutter button remotely:

Set the camera to "continuous shutter" mode, and duct-tape the shutter button down (simple, light, but takes several pictures per second, which uses up lots of battery power).
Set up a little solenoid button pusher (complicated and heavy, but works)
Rig a long string to a button-pushing lever (not very reliable, and the string gets tangled)
Open the camera, solder on wires to the shutter button, and run the wires outside the camera (works great, and can be made extremely lightweight, but remember the shutter button usually presses halfway down for focus, and opening the camera voids the warranty!). For the experiment below, I ran the camera-shutter wires out to a little 8-pin PIC 12F675 microcontroller, running this little button-pusher program. This made the camera automatically take a picture every 2.5 seconds.
Here are some photos we took from the photo pole:

aquisition mbs reichardt reshalls wood_center

Loft a camera using a big balloon.

First, buy some big balloons--36 inch balloons were what we used, and they only cost a few bucks each.
Second, fill the balloons with helium, which you can buy at a party store along with the big balloons (should be $10 or so).
Now tie the camera on to the balloon, and let 'er go! Hmmm... Wait a second...
To pull the balloon and camera back in, you'll need some sort of tether. Fishing line works pretty well to hold the balloon down, and a fishing pole works really well to let the line out and pull it back in. We used 200lb test Kevlar fishing line.
Here are some photos we took using Neal Brown's balloons and fishing rod setup:

duckering ground museum_to_GI reichart wood_center

Build a pinhole camera. This actually didn't work very well when we tried it. It works way better with:

A dark eyeshield or hood to block out light arriving from behind the camera.
(and/or) A small converging lens, like a magnifying glass, in the camera aperture.

Build an infrared camera. (Or get some welding goggles, and use your infrared-sensitive eyes!)

Start with a cheapo webcam that has terrible-looking color--like where black objects look blue or purple. These cameras are usually missing an infrared filter, so the infrared light is screwing up the colors of stuff. If you block out the visible light, the camera will then see only in infrared.
So block out all visible light using a piece of exposed, developed color film (the black stuff at the end of your rolls of photos). Color film has pigments which absorb each color, leaving only infrared. You may need to overlap two or three layers to get a good IR response.
Take normal pictures using the camera--now you're seeing in IR!
Or, if you have several thousand spare dollars, buy a much cooler thermal infrared camera, which operates in the far-infrared regime. At that wavelength, even objects at room temperature are hot enough to glow--and a human being is white-hot!

Here are some near-infrared homemade pictures of trees (which reflect strongly in infrared), asphalt shingles (which are dark and absorb infrared, getting hot), colored marker pens (which don't reflect much IR at all), and automobile glass (which strongly absorbs infrared--one reason why cars parked in the sun get so hot!).

1color 1ir 2color 2ir autoglass

Using a flatbed scanner, scan your hand or face while sliding, wiggling, or rotating it as the scan head passes by. Scanners have a weird non-pinhole perspective, where things get darker and narrower, but do not change vertical size, as they get further away.

lawlerchaun quarter

3D Modeling

Google Sketchup is a nice little 3D modeler with a very friendly interface. You start by drawing a 2D rectangle (or any closed flat shape), and then use the "Push/Pull" tool to sweep the rectangle up into 3D. To see the beauty of Sketchup in action, watch this little tutorial video. Cool, eh? Now download it and follow along with the tutorials or the manual.

To texture a building face, first choose the menu item "Tools" -> "Materials". Add a new material by clicking the weird "+" icon on the top right of the Materials toolbar. Drag your texture image onto the "Texture filename" box. Click "OK" to make a new material with that texture. Hit "Edit" to set the texture size to a reasonable value--by default, textures are only one foot across, but a building photo is usually at least a hundred feet across. Use the paint bucket to apply your new texture to a building face. Right-click on the new texture, and choose the menu item "Texture" -> "Position". This brings up four pushpins. Drag the red pushpin first (to set the texture origin), then the green pushpin (to set the texture scale), and finally the blue pushpin (to set the texture height). I don't recommend messing with the yellow pushpin. Choose the arrow tool again. OK! You've got a properly-aligned texture face!

One thing Sketchup doesn't do well at all is photo texturing on building surfaces, when your photo needs some perspective correction. Here's how I do perspective correction:

Find a good photo of the building face you want. Look for one without interfering objects (like the cursed trees and bushes), and with a reasonable angle.
Open the photo in the GIMP, my favorite free image editor and Photoshop clone. I usually do this by dragging the photo onto the GIMP tools, since I don't like GIMP's "Open..." box.
Crop the photo with the X-acto blade tool. This speeds up the next step.
Choose the perspective tool (looks like a trapezoid). Make sure the perspective tool is in "Backward (corrective)" mode. Drag around the corners of the image to match the corners of the building wall you want to extract. You can zoom in and out with the "+" and "-" keys for precise alignment. Press "Transform", and the perspective tool will distort the selected region to fill the screen.
You might hit "Image" -> "Scale Image..." to set the image to be only a few hundred pixels across. Huge images aren't usually needed for texturing.
Here's an example of how to do this. Note the final perspective-corrected image is now entirely suitable for use as a SketchUp texture.

chapman drag_handles perspectived

For "real" 3D modeling, use a really hard-to-use program like Blender.

External Links

Dr. Orion Sky Lawlor, olawlor@acm.org, 2007-07-07