Is the frozen time bridge the most performance hungry part o

[invictius]

...f any level ever made? (Barring nuts and other wads that pile enemies on) I just see it mentioned a lot and don't think I've come across anything as stressful to a modern pc, other than spacedm9 in opengl instead of software (I can ALMOST run it lag-free)

[Rachael]

Frozen Time is the perfect example of how NOT to map your bridges.

Nevertheless, it was done that way, and it does make for a great profiling tool to test renderer setups and drawing. In fact, it was the go-to map for fixing problems in 3DGE and QZDoom.

Beyond that, it's nothing particularly special. I am sure there's worse. Frozen Time is a very pretty map overall, though, so it's worth enduring a little bit of pain getting it to work if at the very least you have these nice visuals.

[Gez]

The bridge causes a lot of overdraw (like, really a lot), but the worst thing for performance is that pretty much the entire map is made of two-sided lines. Look at this. The engine has got to process every subsector and line segment that is in the field of vision, even when they're not actually visible (because of height differences, for example) until it meets a one-sided line. So you can guess the effect for performances when you have that much open space.

As a point of reference, the Doom Wiki lists these statistics for the map:
Linedefs 26731
Sidedefs 49467
Now if I'm not too bad at maths, that means that there are 3995 one-sided lines and 22736 two-sided lines. (22736*2=45472 sides, +3995=49467, checks out.) That means that the level is over 85% two-sided! Even worse if there's sidedef compression going on, because then the real amount of sides is even larger, which means even more two-sided lines and even one-sided ones.

All this digression to say that even if you simplify the bridges considerably, the level will still cause performance problems.

[Enjay]

As Gez says, it's not just the bridge. I played a version of the map with a "fixed" bridge and even then the complex architecture beyond (made of loads of 2S lines - all visible at one time) still had a noticeable speed impact.

The map should maybe be renamed Frozen PC.

[Rachael]

The map should maybe be renamed Frozen PC.

Coincidentally, that was literally its actual nickname among myself, dpJudas, and Coraline, while fixing our respective ports to work with it.

[Graf Zahl]

All this digression to say that even if you simplify the bridges considerably, the level will still cause performance problems.

I did just that for my play version and replaced all crossbeam bridges with 3D floors. It now plays at 60fps without any hiccups in OpenGL.
Uncapped it's 63 fps vs. 48 fps for the crossbeam version. This map is really just a textbook example of what not to do if you want to have good performance.