The best way I found is to use the CylindricalUVs node and then blending between the planar projection at the poles and the spherical projection around the equator. Kinda old thread, but I figured I’d post my solution here if anyone runs into the same issue as I did. Attached is a partial of my material. It has multiple CylindricalUVs as I am also switching between diffrent materials depending on the height of the terrain. Note that if you want to apply this to normals, you need to make your own custom variant of CylindricalUVs as the default samplers it uses are color based instead of normal based.
This is the result (textures disabled in favor of simple colors and using normals instead)
As to OP’s question about height blend: Use the distance between Absolute World Position and Actor or Object position, then divide that by a combination of object scale, a height bias and the minimum and maximum elevation of your planet procedural mesh (which you are gonna have to pass to the material from the main BP)
