No model or blue prints to go from just eyeballing it , playing with the proportions as i go, been doing this so long now i can get them pretty close these days by eye, for the more detailed bits, i'll block the basic shape out first until i'm happy with the proportions then add the details after. I've got some reference images im using as a guide, but there aren't , or atleast i couldn't find any high res images of him in the mk 4 suit from the first game and any images of the game model are as you'd expect from a game that came out 20 years ago nearly, quite poor, there are images from the blackmesa remake but the suit is quite different and i wanted to keep it as close to the original as possible.
i did manage to find some images for a female version of the suit, that someone posted on mod db from a few years back, that and some game art are the main images im working from. This is sort of a blend of the two along with some of my styling. pretty fun project, i've moved away from the more detailed models recently the last few years, apart from work related stuff. mainly down to the amount of time they take, so this is a nice change of pace to get back to a little bit of that.