Well, the free roaming areas are usually pretty small, a room or a street corner. The movement is also very relaxed, or even slow. It also takes time for anything to happen after you interact with an item as the game has to load the animation for it. Not very efficient on a fast paced shooter where the whole map gets loaded into the memory at once.

That makes sense. Still, it looks amazing for 1994, better than even something like Half Life to be honest. I wonder how good could a modern story driven adventure look if these limitations were respected, maybe near photorealistic (I don't consider the graphics of modern games to be anywhere near photorealiatic).

Rise of the Triad tried to use some of those realistic models in a shooter, also Realms of the Haunting 2 years later. IMHO, neither of them look that good or work that well. I was never a fan of the whole digitized sprites concept, it made everything look rather cheap.

That is not what I am talking about through. I am talking about the explorable 3D enviroments. It could run on a 486 in 640x480, something that Quake needs a Pentium 2 for.

Basically, I am asking how a game could have had almost Counter Strike level graphics (in the interactive parts), in a realtime fully interactive 3D engine, in 1994.

The engine was a lot simpler than Quake for one. Like sf78 said, the areas are small, much smaller than a level of Quake. On top of that, most of the objects are not really 3D, they are essentially sprites. You have to remind yourself that Quake was often marketed as the first fully 3D FPS game, although even that is false (all of the explosions are sprites for example!). But, it was attempting to do a lot of really groundbreaking and impressive stuff at the time. I don't know where you get the Counter Strike analogy from, in my eyes UAKM doesn't look that much more advanced than Doom or Dark Forces.

Also, UAKM at 640x480 on a 486 is unplayable. Even on a Pentium MMX 200-233 it can be slow at 640x480. I know I needed a Pentium III 500 to enjoy its sequel, the Pandora Directive, at 640x480 🤣 .
That being said, you can run Quake at 640x480 with an MMX 233 or so and I would say that the experience would arguably be on par or faster than UAKM is on a 486 at the same resolution.

Doom or Dark Forces are not truly 3D like UaKM. Also, I have a feeling that you are one of the "60 fps or bust gamers" if you describe it as unplayable on a 486 in SVGA, most gaming magazines of the timr describe it as playable in SVGA on a 486. In 1994 60 fps was a dream in 3D, even 30 fps was rare.Still, a233 Mhz MMX is 10x faster than a 486DX2/66.

I am, but that's besides the point, since I did compare it to Quake at 640x480 on an MMX 233, which is something I would not play btw, and said that the latter experience would arguably be finer, even taking into account that UAKM doesn't rely on twitch reflexes and can be very enjoyable even at lower framerates. So, that was some nice goalpost shifting on your side, I enjoyed it greatly. I have a feeling you are one of those "15-20 fps is fine" gamers.

Since I happen to have an unbelievable amount of time on my hands at the present time, I will take you up on this challenge and emulate a 486 by disabling caches on my K6-III+ and run my copy of UAKM on it. Who knows, I might even attempt Pandora Directive, one of my all time favorite games.

By the way, even on the Pentium III 500, Pandora Directive could not maintain 60fps at all times 😀 .

Took me a while to edit, but here it is:
https://youtu.be/UpgYf3r8PzU