This old FPS game had ridiculous, but technologically remarkable model damage effects:
I think you are talking of “Vivisector: Beast Within”… and it seems they simply modeled
and this individual for every part of the body then simply switch the mesh (or even making the outer one simply transparent). For 1/2 and 3/4 maybe even only switching texture (for example making fur image boards ). The switching seems to be also “covered” by some visual effects.
So you think gore was completely handcrafted, like they simply modeled the meat layer as multiple small fragments? That makes sense, though their engine was advertised as being able to alter geometry on the fly. Advertisement bullshit perhaps
I do not know what they said about “altering on the fly” but of course any alteration has to be descripted (with different modelled shapes and or textures… or even with shaders) in some way… no engine can do any magic 
vivisector gore system.blend (2.2 MB)
I tried to do this effect in semi-procedural way:
Well, after I’ve looked up what was said in the presentation, it indeed could be that “altering complex geometry” refered to Action Forms’ in house level editing tool rather than realtime effects.
Ooh, the cover for this game (the one with the lion) looks like it would fit on a metal album. Nice.
I’d partially agree with oki’s assessment: there seem to be 2 models - flesh and skeleton. The flesh part seems to be pre-devided in fixed chunks though? Like if you shoot at the shoulder it will always peel off the same way… maybe - can’t really tell from gameplay that I found. And so you can design the edge of the “holes” when you decide on topology.
Of course, this system does not account for clothes and cybernetics at all…
I never played this game, but from the videos I’ve seen, it seems that they just use a decal texture as a transparency mask to reveal other geometry inside the bodies, and not a full geometry segmentation thing (that would be an expensive calculation for that time).
I did play the game though. Definitely did not look like zero thickness mesh + transparency for me. Holes in the bodies clearly had polygonal boundaries like in my GN example. So either all meat chunks were premodeled or there was some procedural system
Okay, even if it is possible to do it procedurally, pre-modeling all the chunks seems to be better solution for in-game use
Have you played Killing Floor 2? They had MEAT system. From what I gather, every enemy has over a dozen pre-made points (of which more than one in the head), that can be blown off. In-game it can look very… gory, yes, but just enough so to be exciting, instead of completely revolting. Yay for artistic control 
Plus you’re less likely to see meat chunks falling off metal 
Another similar system:
No, I yet have to play it to see it. Not much is clear from the videos
That’s very detailed gore, unfortunately not much about technical side. Unclear if the flesh part is simply displaced inwards or there is more sophisticated algorithm. I still got some ideas from it. From what they told about intestines being the same in all causes, they must’ve fitting the internal structure model inside every zombie variation procedurally, based on the skeletal joint positions.
I’ll have to experiment with the meat layer’s topology for cleaner holes. Cris-crossing every quad gives better results. I only need some heuristics to remove solitary triangles. 
In this article there was something about “shooting holes through zombies”, so I guess the outer layer is removed/turned invisible somehow, not displaced.
Right, I’ve forgot. So either a mesh made of prisms like I’ve tried already, or perhaps multiple shells which appear contigious through some rendering trickery
