Differences between complevels 7, 8, and 9?

[maxmanium]

What are the differences between these complevels? I don't see them documented anywhere -- I know what they represent but what's the actual difference in game logic?

 

While I'm at it, what the hell is the "demo insurance" option in Boom\MBF?

Edited June 5, 2021 by maxmanium

[Redneckerz]

8 hours ago, maxmanium said:

What are the differences between these complevels? I don't see them documented anywhere -- I know what they represent but what's the actual difference in game logic?

Quote

It is from PrBoom.

 

Quote

COMPATIBILITY LEVELS

Demo recorders should read this carefully. These complevels all work both for recording and playback.

 

If you use a complevel for playback, it will override the autodetection of the demo type. This is useful to handle cases in which autodetection does not correctly identify the demo-type. Autodetection will still work for the vast majority of demos.

 

Number Name Description

• 0 doom_12_compatibility Partial (improved) emulation of Doom.exe v1.2
• 1 doom_1666_compatibility Partial emulation of Doom.exe/Doom2.exe v1.666
• 2 doom2_19_compatibility Emulates the original Doom.exe v1.9 & Doom2's doom2.exe v1.9
• 3 ultdoom_compatibility Emulates Ultimate Doom v1.9 and Doom95
• 4 finaldoom_compatibility Emulates Final Doom's doom2.exe
• 5 dosdoom_compatibility Emulates Dosdoom .47
• 6 tasdoom_compatibility Emulates Tasdoom.exe
• 7 boom_compatibility_compatibility Emulates Boom's compatibility mode
• 8 boom_201_compatibility Emulates Boom v2.01
• 9 boom_202_compatibility Emulates Boom v2.02
• 10 lxdoom_1_compatibility Emulates LxDoom v1.4.x
• 11 mbf_compatibility Emulates MBF
• 12 prboom_1_compatibility Emulates PrBoom v2.03beta
• 13 prboom_2_compatibility Emulates PrBoom v2.1.0
• 14 prboom_3_compatibility Emulates PrBoom v2.1.1-2.2.6
• 15 prboom_4_compatibility Emulates PrBoom v2.3.x
• 16 prboom_5_compatibility Emulates PrBoom v2.4.0
• 17 prboom_6_compatibility Latest PrBoom-plus
• -1 default_compatibility_level Current Prboom-plus

Here's a quick summary of the most important ones for recording:

• -complevel 2 - "vanilla" Doom2.exe
• -complevel 3 - "vanilla" Ultimate Doom.exe
• -complevel 9 - Boom
• -complevel -1 - current Prboom+

 

8 hours ago, maxmanium said:

 

While I'm at it, what the hell is the "demo insurance" option in Boom\MBF?

What it says: insures demo compatibility?

[maxmanium]

50 minutes ago, Redneckerz said:

It is from PrBoom.

 

I know, I think I really meant to ask what's different about complevel 7 from 2 or 3. As for 8 I thought Boom 2.01 and 2.02 were identical aside from licensing or something?

 

50 minutes ago, Redneckerz said:

What it says: insures demo compatibility?

 

Sure, but what's it actually doing? I don't think this feature is present in modern source ports so I just don't understand what it's actually changing in terms of game logic.

Edited June 6, 2021 by maxmanium

[Shepardus]

Here are some changelogs for Boom 2.02 and 2.01.

 

This is what boom.txt in the prboom-plus docs has to say about demo_insurance:

 

Quote

2) Demos

BOOM supports demos made with previous engines in a limited fashion.

Some will go out of sync, though none will cause the engine to crash. This

is almost unavoidable due to the large number of changes made in the engine.

Internal demos may now contain revenants without losing sync.

 

The demo_insurance option in BOOM.CFG allows one to make tradeoffs between

demo sync and game chaos. If demo_insurance=0, Boom demos stand a good chance

of losing sync on the next version of Boom, but the gameplay is more chaotic

because a single RNG is used for all events. If demo_insurance=1, Boom demos

stand a greater likelihood of staying in sync across Boom versions, but the

game is slightly less chaotic as a result. The two goals of demo sync across

different versions of the game, and chaos during the game, are somewhat

contradictory. If demo_insurance=2 (the default), then the special steps are

only taken when demos are being recorded -- normal gameplay is unaffected.

 

demo_insurance does not affect the playback quality of Doom demos, which were

recorded without Boom's special sync-preserving measures.

 

Even when demo_insurance is enabled, the games are fully randomized -- the only

difference is whether independent game events will use the same RNG and thus

interact, increasing the chance of demo desync if the slightest change occurs

in the game, or whether each game event will use its own independent RNG.

Looking at the code, I can see it's used in the RNG, but I'm not sure exactly what for. In any case, it's a relic of Boom and I'd recommend not touching the setting.

Edited June 6, 2021 by Shepardus

[Dreemurr Deceevurr]

Doom Wiki says that complevel 7 emulates Boom (presumably 2.01/2)'s vanilla compat mode, which is apparently inaccurate. I'm curious to know how inaccurate it is compared to complevels 2, 3 and 4.