Position of a contact point, d_i is the position vector w.r.t the global reference frame. And it is reported by U-sub for Soil Interaction. d_i is calculated as follows.

Where is the orientation matrix of the action geometry reference frame, r is the position vector of and is the distance vector from position of to a contact point w.r.t .

Contact force at a contact point is the force vector with regards to the contact reference frame. And it is reported by U-sub for Soil Interaction. Contact force at a contact point,

is calculated as follows.

where i is the contact point sequence, is the orientation metrix of a contact reference frame, a is the area of a contact point, τ is the shear pressure and p is the normal pressure at the contact point.

The contact force () that occurs in the normal direction between the body and the soil uses a formula similar to that for general contact (see Intermittent Contact Force in the Motion Theory Reference). The difference is that , referred to as the bounce-off damping factor, is zero for soil interaction.

Total soil interaction force is reported by Vector Force entity. Total Soil Interaction force, f is calculated as follows.

Where, n is the number of the contact point, i is the contact point sequence, is the orientation matrix of the contact reference frame and is the soil interaction force of a contact point w.r.t .

Total soil interaction torque is reported by Vector Force entity. Total Soil Interaction torque, is calculated as follows.

Where is the distance vector from center of the geometry reference frame to a contact point with regards to the global reference frame.