Each episode of the “Crime 360°” reality program on A&E TV features the very expensive Leica Scan Station.
by Wayne Cole
This 3D laser scanning system captures a point cloud within a spherical domain around the unit that can be turned into a 3D model of an incident scene. The Scan Station can be used indoors or out. Software can take photos from the scene, and texture map them into the 3D scene. As a theory of the incident takes shape, video techs can add humanoid figures and props such as weapons and vehicles that can be used to animate a reconstruction of the incident complete with interactive “movement” and zooming throughout the scene.
Users can click “hot spots” in the scene that link to relevant evidence files (photos, finger prints, measurement data). Other advanced features make these very expensive systems worth their price for high-volume forensics, civil engineering, architecture, and “virtual tour” applications.
But in this economy, many agencies and independent technicians do not have the budget for systems like the Scan Station. However, if you have a video or digital still camera, Adobe Photoshop CS4 Extended, and a modest budget for other software tools, you can create your own panoramas and interactive, hyperlinked experiences without much effort.
THE TIGHT SPACE CHEAT
Many incident scenes that must be visually documented involve close quarters, like rooms in all manner of residences. Ultra-wide angle lenses can give a complete view of the area, but often have unacceptable levels of distortion that make the scene difficult to “read.” With a “normal” or mildly wide angle lens, however, you can stitch multiple images together to provide a comprehensive scene overview. Photoshop makes this a snap even for handheld shots. In the “crime scene” that is a small office I made an acceptable room view by shooting two digital stills from one corner of the room.
Starting with two photos with overlapping details… To allow Photoshop’s Photomerge tool to work you need to be sure there is overlap between the pictures with sufficient detail so that the pictures can be lined up. You create a new panorama simply by selecting File-> Automate-> Photomerge. A dialog appears where you can select the layout (auto, cylindrical, spherical, perspective, for example) and the images to merge.
The “Blend Images Together” option will make the stitching seamless, and adjust the images’ exposures and color balances for the best match. You can also select options for automatic lens vignette and geometric distortion correction. Then select “OK.”
Depending on the number of images to stitch and the horsepower of your system, it will take from one to several minutes to create the panorama. However, it is fast enough that you may want to try other layouts to see which gives the best result.
Photomerge usually produces a panorama that does not exactly fit the rectangular dimensions of the Photoshop canvas. To make a clean rectangular picture you can crop away the irregular edges produced by the bending and merging required to fit the pictures together. You will lose some of the image, but you will generally have extra material at the edges that you can crop away without compromising the value of the final image. For this and other reasons, when using a still camera for a panorama it is best to shoot each image in portrait orientation.
GOING FULL CIRCLE
The “right way” to capture imagery for a 360-degree with standard equipment is to mount the camera on a tripod with the tilt and lens zoom locked, then pan around the circle stopping at constant 15° to 40° intervals to capture a still which has some overlap with its neighbors. Some stitching programs will only work if you shoot this way. But Photoshop is VERY forgiving.
…You can create your own seamless panaromas I shot a 360° set of stills in a residential back yard, hand held, in landscape mode, turning enough in each shot to just maintain some overlap. I also used auto exposure. All of these actions would be enough to send most photo stitchers into manual alignment mode. But not Photomerge.
Simply selecting the images in left-to-right order, the layout, the blend images options and letting Photoshop work, I produced useable results with both the “Auto” and “Cylindrical” layouts.
The next step involves cropping away the blank spaces. Then you need to trim the left and right edges so the can seamlessly match when you wrap the image into a 360-degree view in a panoramic viewer.
There are several ways to do this. The easiest, however, is to download the free Panoramicsrev3.zip file which contains a Photoshop action script to do this for you.
Here you have good multiplatform options: QuickTime VR, Java or Flash. QuickTime, Java and Flash viewers can be found on the internet for free. However, you will generally need to spend some money ($35 to $300) for a tool to “author” in one of those formats. You can spend even more if you want to create complete virtual tours. But even the less expensive tools offer the ability to define “hot spots” so that, when mouse-clicked, you can link to other panoramas or perform some other action.
For a back yard panorama, I used Panorama Factory 32-bit version to create a QuickTime VR. (QuickTime does not provide 64-bit support). Panorama Factory can also output to a file format compatible with most Java-based viewers like PTViewer. Many of the more expensive tools like VR Worx include photo stitchers which are unnecessary if you already have Photoshop CS4. Pano2VR is a tool that can also output to Flash. So there are a lot of choices depending on the format you need for the consumers of your panoramas. Also, note that at this time, QuickTime VR does not work on Windows 7, so that may factor into your plans. But, as you can see, there is a way to produce very functional and valuable panoramas on a shoestring budget.