That was set up by one of the rendering artists in the shader graph using the (Get Skeletal Mesh Embedded Positions) node. The idea involves taking the sample positions from the simulation (see Sampling Simulation Results) and using those to build a 2D texture to drive the deformations of the Nanite model. The map is generated by finding the distance between the sampled simulated position from its initial “pre-simulated” position, and then blending those deltas across the UV space of the deformation map. The float values in the deformation map are used as a scalar to displace vertices along the direction of the vertex normal.
There are limitations with this approach in that they only capture displacement in a single direction, so the accuracy of the transfer is tied to the placement of the sample positions relative to the render vertices. This worked for the Rivian tire because the sample positions we used to capture the deformations transferred to the texture reasonably well. There might be a general solution in the transfer process, but we did not take our implementation that far, as it seems like something that should be optimized on a case-by-case basis.