I thought we've reached the bottom of how fucking bad Rev60 is but whenever Wu opens his mouth I go "waaait" and discover that it's possible to go deeper.
Wu was "level designer", sure, I can buy that he was constructing a lot of that boring, primitive, bland and shapeless bullshit, just look at how bad this is:
Ignoring the horror of the colors and characters everything is so boxy and angular, as if they were... BSP brushes! Those are fucking BSP brushes, Wu, you mong, they shouldn't be used for anything other than sketching out a rough shape of a level then removed and replaced with static meshes. Because BSP brushes are very slow and inefficient and Unreal Engine transitioned away from using them after UE2. No wonder the game had performance problems.
The not-as-unreal-experts at Epic puts it this way in their documentation.
Geometry Brushes are the most basic tool for level construction in Unreal. Conceptually, it is best to think of a Geometry Brush as filling in and carving out volumes of space in your level. Long ago, Geometry Brushes were used as the primary building block in level design. Now, however, that role has been passed on to Static Meshes, which are far more efficient. However, Geometry Brushes can still be useful in the early stages of a product for rapid prototyping of levels and objects, as well as for level construction by those who do not have access to 3D modeling tools. This document goes over the use of Geometry Brushes and how they can utilized in your levels.
That's why everything looks like it has been carved out with a bandsaw and and crudely mangled by boolean operations, just like in Quake or every older games that did the same. All this time I just thought it was really ugly and made by a moron with no taste.
I'm not sure of the performance impact but these geometry brushes vs static meshes could mean that tens of polygons in a geometry brush might take the same time to set up and render as a thousand polygons in a single static mesh. But I don't really know, I just get the impression that it might be a draw call issue relating to how geometry brushes are broken down, pure speculation. Draw calls could be thought of as a transaction fee, the cost to start the render of an object, a high transaction fee with a small purchase repeated many times is not good and it's the CPU that is fronting the cost, so while graphics performance might seem slow it is usually not because the GPU can't keep up, it might spend time idling, waiting for something to do.
It was always a mystery why Rev60 ran like shit despite looking like shit and this might be why.
(one of the bullet points of Vulkan and DX12 was getting rid of the draw call overhead to increase performance).
Another major drawback of this type of geometry is that texture mapping sucks and is really basic. These are promotional screenshots so expect less mismatched seams and improperly aligned textures, but there's still some showing, partially due to the texture artist being really bad but primitive UV mapping sure doesn't help.
That geometry. Thief, Quake, Sin, Half-Life Deus Ex, they looked way better but it is very similar.
The hole in the rafters, that's made with a subtractive brush, meaning that a shape is put in another shape and the shape of one is subtracted from the other, something that is much more inefficient than just constructing it from scratch to look that way because after the subtraction it will likely be made up of many more polygons than necessary and with these brushes that's really not good. Looking at the screenshots again I suppose that function was used a lot.