It looks like they just used some upscaler on the original graphics which is a shame; missed opportunity there. It would have been really cool to see the original models / scenes rendered at high resolution in 24-bit color with modern lighting algorithms. Those assets are probably long gone though.

Or just re-construct the mansion in Unreal or Unity a la RealMyst... 😜

TBH I really like what the Night Trap team did for their HD re-release, but AFAIK they had the original FILM footage to re-scan & re-master.