How to transfer normal information for tree canopy as they did in Horizon Zero Dawn

Hi all
I was watching the Guerrilla GDC talk, where they mention about transferring normals from a blob surrounding the tree canopy onto the tree. I noticed they mention “…we use an ISO service to generate our normals”. Below is the screenshot they shared showing the blob mesh with normals


Is there a way to so something similar in Unreal Engine? I would love to know about this since it is very hard to modify a mesh that was imported from Speedtree 9 with wind effects. If I do any edits to the mesh in an external program, it breaks wind.
If I can do the normal transfer inside Unreal, that would be amazing.
Thanks and let me know