Freedom VR

An introduction to VR photography

Although many companies sell expensive and specialized equipment for VR photography, anybody with an inexpensive camera and a measuring tape can take VR photographs outdoors; like any other kind of photography, you'll need to shoot a few rolls of film for practice but you'll soon be surprised at your results. It's easy, we're beginners at photography ourselves. Better photgraphers with better cameras can certainly pick up the ball and develop more advanced techniques. You can see our work in Paul and Olivia's VR Garden. We've made a collection of models other people have made using conventional cameras, digital cameras, video cameras and computer synthetic images on our Freedom VR Samples page.

There are two kinds of VR photograph. In one kind you're in the middle of a panoramic scene, and in the other you spin an object around. This page explains a technique we've developed to make the second kind outdoors. Our technique is a bit of a hybrid, because photographing an object in it's natural environment captures both the object and it's environment.

You should be able to take panoramas using a similar technique; you must take a number of pictures from a single spot at different angles. We're planning on trying this as soon as we get a tripod. We're told that one needs at least nine photographs. We don't currently have software for stitching individual frames into a panorama which can be smoothly scrolled, but we may write this in the future. The illusion of three dimensions can still be constructed effectively with just a series of photographs -- the illusion is created by the same perceptual process that closes the gaps between frames in a movie.

What you'll need

A tripod would probably help, but we don't have one yet. Our current equipment fits in a backpack so we can take VR photographs anywhere. [vr stage]

The VR stage

A photogaphic VR model is a series of photographs taken of an object from precise locations. To establish precise control of space outdoors, one sets up a VR stage. To build a VR stage, you lay out a regular polygon on the ground. You have to make two choices at this point; first, the number of photos you'd like to take and secondly, the radius of the VR stage. For most of our models we've used 12 pictures. The more you use, the smoother your model will rotate -- however, more pictures will make your model bigger, so it will take more time to download. You can decide what radius to use by looking at the object through the viewfinder and deciding what would look best. Don't forget that you're free to rotate the camera; we've made great VR models holding the camera both normally and sideways.

He're how to lay out an accurate VR stage with turf nails and a tape measure. The picture below explains the geometry.

[vr stage geometry]
Figure 2

The radius of the VR stage is r. Lay out the first stake at distance r from the object in a direction you choose. To place the second stake, you next compute x, the distance between the first stake and the second. The equation is

N is the number of photos. To solve this on your calculator, divide 180 degrees by N. Hit the sine button, multiply by 2, and multiply by r. The answer is x. (For the special case N=12 you can just multiply r by 0.51763.)

From basic geometry, there are only two points on the ground that are simultaneously at a distance r from the tree and at a distance x from the first stake, one one each side of the stake. Now, suppose you stretch out your tape measure along the heavy line in the figure above -- the distance to the corner is r and the total length of the tape measure is r+x.. Attach the end of the tape measure to the object (or a nail near the object) and attach the point on the tape at length r+x to the first stake. Hold the tape measure at point r and drag it taught -- drive in the second stake at the corner of the tape measure, and repeat until you've made a circle. We're often accurate to within a few inches with this method -- if we're a little bit off at the end, we put the last stake halfway between it's neighbors to spread out the position error.

Taking the photos

You've just built a circle of stakes around the object. Taking photos is straightforward. Aim for an imaginary point near the center of the object. If you learn to be consistent, you can do well without a tripod. Since you'll be taking pictures at all angles, you won't want to do this early in the morning or late in the afternoon on a sunny day else you'll take some of your photos into the sun. We've taken our best models under overcast or during our lunch breaks. You'll also have to worry about continuity -- it is best to avoid photographing people or other moving objects in the background.

Digitizing the photos

After taking the photos, you'll have to get them into the computer. If you've got a digitial camera no problem -- the rest of us have several options. If you have a scanner, you can scan the prints in yourself. If you don't have a scanner or don't want to spend time scanning photos, any Konica dealer can scan your photos for you and put them on a floppy or on the web for a reasonable price. (find out more) The web version is compatible with everything, the floppy version uses a propreitary image format which you won't be able to read with a Unix machine. We've been pleased with Konica's service. The Kodak Photo CD is higher quality, but costs much more and takes longer.

Preparing the photos

Once you've digitized the photographs, you must make them all the same size. You can accomplish this by rescaling and/or cropping the images. Because most people still have slow network connections, you'll probably want to reduce the size of your photos. Chances are your photos will not match perfectly in brightness and color balance and there may be minor blemishes. You can fix this with an image editing program. PC and Mac users will probably use a commercial program like Adobe Photoshop; on Unix, I like the command line convenience of ImageMagick which can rescale or brighten a whole directory of images with one easy command. The GIMP is a powerful interactive image editor for Unix.

Building the model

The last step is to put the photos together to make a VR model. We've developed the free Freedom VR applet to do this for you. Freedom VR is free and works on all platforms. If you can make web pages, you can produce Freedom VR content -- Freedom VR models appear automatically in any java enabled web browser (such as Netscape Communicator) without downloading any plug-ins or helper applications. There are some commercial options, but an examination of the facts reveals that few compete with Freedom VR. Quicktime VR content can be viewed by Windows and Mac users if they download a special plug-in. There are no authoring tools for Quicktime VR on platforms other than MacOS, so this is not an option for Unix or Windows users. Although Quicktime is claimed to support sophisticated multimedia compression, we've found that we get better compression with JPEG than with any of the Quicktime codecs. NetVR is an company located near the the railroad tracks in Redmond, WA; we don't know if they have any connection with Microsoft. NetVR has an applet called "turnado" which is similar to Freedom VR except "turnado" objects cost $50.00 each.
 

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