In this model, the tilt component of the tilt and torsion angle system is modelled simply as

θ≤θ_{max}. |
(16.21) |

The torsion angle restriction of 12.76 on page is used for the modelling of the torsion component. A uniform distribution of rigid body positions within these bounds is assumed.

The isotropic cone model of the ball and socket joint consists of a single pivot point, a single unit z-vector of the motional eigenframe defining the cone axis, and the maximum cone opening and torsion half-angles. Including the average domain position, the parameter set is therefore

where *P*_{i} are the average domain position translations and rotations, *E*_{i} are the spherical angles defining the cone axis, *p*_{i} are the coordinates of the pivot point, and
*θ*_{max} and
*σ*_{max} are the maximum cone opening and torsion half-angles respectively.

The relax user manual (PDF), created 2019-03-08.