Modeling 1: Polygons - An Introduction to Computer Graphics for Artists - page 81

Fig. 6.9 Escape-Proof Prison © 2011 Andrew Paquette

6.5.4 Set Camera

After you have a background image in the scene as reference and have checked that
its aspect ratio is correct, build a reference cube in your scene. The reference cube
should be about as large as the largest structures in your scene. It is important to
make it large rather than small, because it will be easier to detect errors. Display the
cube as wireframe only so that you can see it in front of your reference image
(Fig. 6.13 ).
Next, adjust the focal length of the camera until perpendicular angles in the
drawing appear to match perpendicular angles in the cube. Check the top and bot-
tom of the cube. It is possible to align one without aligning the other. For the camera
to work, both must match. If you must, rotate the camera to assist in lining up the
cube with the major perpendicular and parallel lines in the reference image. All of
the drawings provided use different types of cameras. Some are orthographic, some
are perspective. Depending on the drawing you are using, you may have to offset
the camera relative to the reference drawing. This is required when the drawing is
like a cropped photo that represents some portion of an image that is off-center rela-
tive to the camera's center of focus.