The camera looks at one of the corners of the cube. To solve this problem we have to pre-distort the texture. The rest of this text describes three such distortion techniques. Now assume that a sphere with radius 1 is contained within a cube with side length 1, both centered at the origin. We then use them to index the background image.
Several solutions are possible.
Figure 3 depicts another approach. If the cube is cut open, we get the result shown to the right in figure 3. Therefore, some care should be taken when drawing them. The result is shown in figure 5. The drawback of the spherical projection method is obviously the way the 'up' and 'down' images are distorted.