2. Camera Matching
In order to add 3D objects to one of 3six0's background photographs, it is necessary to create a camera in the 3D scene that mimics the real-life properties and orientation of the camera used to take the photograph.
The following steps will help to make the camera matching process as straightforward as possible.
a) Set the output resolution in your 3D software to match that of the background image (Figure 06).
Figure 06
If this resolution is too high for your needs, simply ensure that the aspect ratio of the image (width/height)
is identical to that of the photograph. Add the image as an environment map (Rendering>Environment in 3ds max), and
make it visible in one of the viewports (Views>Viewport Background) (Figure 07).
Figure 07
b) With the resolution now set, it is important to ensure that the virtual camera has the same focal length (and optionally
other properties, such as f-stop, shutter speed, etc.) as the real-life camera.
This information is included in the background image file in the form of exif data. This data is displayed alongside each image on 3Six0.net, and can also be found using image editing software. For example, by choosing 'File Info' from the 'File' menu in Adobe Photoshop (Figure 08).
Figure 08
Use this data to set the properties of the camera in your 3D scene*. Some software will only allow you to change the focal
length of the camera, whereas others, such as VRay, will allow you to have far greater control over the camera properties (Figure 09).
*Please bear in mind, that many 3D software packages will interpret the focal length you enter as if the lens were being used with
35mm film.
For some cameras used by 3six0's photographers, such as the Canon EOS-1Ds Mark II, this will give you the correct result.
However, for some cameras with smaller CCDs, entering the focal length found in the exif data will not give the correct result.
If the image you are using was taken with either a Nikon D200 or a Canon 350D, please either enter 22mm as the 'film gate' / 'aperture width'
along with the focal length stated, or multiply the focal length given by 1.6. Do not do both.
Figure 09
c) The only thing left to do now is to adjust the orientation of the camera in relation to the 3D scene. The easiest way of doing this
is create an object in the scene of a similar size and shape to an object in the photograph.
For example, to match the following photograph (Figure 10), a long thin plane was created with roughly the same width as the road in the image.
Figure 10
The camera can then be positioned, either by using the Move and Rotate tools on the camera and its target, or more easily, by activating
the camera view, and using the Dolly, Truck, Orbit and Roll tools (Figure 11).
Figure 11
Now any object you add to the scene should sit realistically in the camera view. It may be worth creating a copy of your camera
in case you accidentally move it whilst working on the scene.