
26.3. SUBSTANCE-BASED DESIGNS 815
(a) circular [Mit94] (b) radial [BW04]
Figure 26.7 Circular and radial drawing.
approaches for layered layout can be adapted to radial levels (Chapter 13 and [Bac07]).
The most recent approach uses stress minimization with a penalty term [BP11] measuring
deviation from the assigned radii. By increasing the relative weight of the penalty term
during iterative stress reduction, vertices are gradually forced to lie on their respective circle.
While it appears that the less severe restrictions to which intermediate layouts are subjected
may provide an advantage over gradient-projection methods, thorough experimentation ...