On the left, the raceways both slide and roll — the red marker shows the sliding side. Roll's custom optimization reshapes the raceways to create pure rolling, on the right.
The rollers slide against the raceway as they travel — the sliding that sheds energy as friction and heat, and wears the surfaces. The motion pauses when the sliding pair switches sides.
Roll's custom numeric methods curve the raceways to eliminate sliding, just pure rolling.
Animation is a kinematic simulation of the rolling interface. Efficiency figures quoted elsewhere on this site are targets, pending physical validation.