5-2 Special mapping equations 185
N
S
r
P
p
O
Q = π(P )
R
O
∗
D
Fig. 5.16. Spherical vertical section, general normal perspective mapping of the sphere to the tangential plane
at the South Pole, projection plane at maximal distance.
The normal perspective mapping, which corresponds to Fig. 5.12, but where the perspective center
O
∗ is placed north on the SN line and the projection plane is identified as the tangent plane at the
North Pole, is presented in Fig. 5.17.
N
S
r
P
p
O
Φ
Q = π(P )
R
R
H
O
∗
D
Fig. 5.17. Spherical vertical section, general normal perspective mapping of the sphere to the tangential plane
which is at minimal distance to O
∗ : D = R + H.