Racing Line (Racegroove) - mapping

Hi,

Im new to track modding, coming from rfactor I used to map the racegroove in 3dsmax using the spline mapping method. I saw a small video on youtube for how it is done for Assetto Corsa (in 3dsmax) but I needed more information to get the job done. I couldnt find much else anywhere so I was hoping if anyone could help me with a little bit more of a detailed procedure for it.

Thanks.