Just to be clear to people not following the link: physical 3D models. But today you could also make electronic 3D models (in, say, Blender) and shoot them from various angles to get sprite images. Later 3D-looking sprite-based games did this.
I assume they rotoscoped over those photos because the images are definitely look hand-edited. Blizzard went similar for Starcraft and Diablo - start with 3D model renderings and then hand-paint over them to get the art pixel-perfect.
They were definitely hand-edited and de-babelized. Would be interesting to have high-res images and edits for the later versions of Doom ports for today's screens, considering Doom ran on a 320x200x256 display.
Yes, it's a set of facing angles, and then mirror'd for the other side. I played with Doom modding tools back in my youth, I've seen the sprite-sheets. The Cacodemon isn't a good example, though, since it doesn't have a walk cycle.
Every monster that can walk needs to have a fully animated walk for going towards the player and away from the player and every angle in between. Ditto firing anims. That's a lot of walk cycles. They cheat with the death anims since the monster always faces the player to die. Still, lots of walk and firing anims.
The approach also fails for PVP models because players can fire and move at the same time, which creates the "skating" effect from Doom/Quake1/Quake2.
It's a lot of work, but there is nothing complicated about getting it done. You tell the art guys the specs and they spend a few days getting all the images and then move on to the next monster.
Why yes, yes I did. But for Doom there were about 10-15 kinds of sprites (monsters, lamps, trash cans). I didn't say it was easy, I said it was straight forward. The code took a lot of time back then, and I'm sure the art guy(s) were busy the whole time.
Indie titles means clever/complicated is better than labour-intensive, because labour-intensive costs money but cleverness just needs one brilliant programmer/artist.
