It is possible to determine the three or four view geometry in a similar way to the two view geometry computation explained in the previous section. More details on these concepts can be found in Section 3.3. Since the points satisfying the three or four view geometry certainly must satisfy the two view geometry, it is often interesting to have a hierarchical approach. In this case the two view geometry is estimated first from consecutive views. Then triplet matches are inferred by comparing two consecutive sets of pair-matches. These triplets are then used in a robust approach similar to the method presented in Section 4.3.4. In this case only 6 triplets of points are needed. A similar approach is possible for the four view geometry.
The method to recover structure and motion presented in the next chapter only relies on the two view geometry. Therefore the interested reader is referred to the literature for more details on the direct computation of three and four view geometric relations. Many authors studied different approaches to compute multi view relations (e.g. [176,65]). Torr and Zisserman [193] have proposed a robust approach to the computation of the three view geometry. Hartley [68] proposed a method to compute the four view geometry.