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fawtytoo said:
Why does Final Doom: Plutonia demo3 go out of sync?

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Maes said:


I'd like to know that too ;-)

The only demos that Mocha Doom plays correctly -to my knowledge- are DEMO2, DEMO3 and DEMO4 from Ultimate Doom, and maybe one or two from TNT or Plutonia.

Considering how it's also a straight derivative of the linuxdoom code, perhaps what's plaguing you right now might help me understand what's going on in general.

However, there are significative differences between the .exes used in UDoom/Plutonia/TNT, enough to cause desync on their own (and they are not codified in the linuxdoom code. Hell, not even the Episode 4 switch textures are!)

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Gez said:
I'd suggest first looking if these demos desync as well in PrBoom+ and/or Chocolate Doom (pretty sure they don't), then looking at the source code from these ports, grepping through them for compatibility code.

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wesleyjohnson said:
The Demo file system is nearly useless across ports and needs to be
replaced with something that is robust. It is only the id games demos
and important WADS with demos that keep us trying to rescue this
system.

I have seriously been considering a self-correcting demo playback.
Of course this won't really work, but have been considering what
it would take.
1. Shooting: Player direction would be corrected for errors to hit the closest target.
2. Pushing a button or door would correct the player direction.
3. Dying in a demo would end the demo.
5. Allow user choice of raw demo or corrected demo playback.

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fawtytoo said:
I'm just looking for heaps of suggestions even if I have to write it myself.

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Gez said:
I'd suggest first looking if these demos desync as well in PrBoom+ and/or Chocolate Doom (pretty sure they don't), then looking at the source code from these ports, grepping through them for compatibility code.

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fawtytoo said:

I'm not convinced that compatibility is the cause.

I have a wad compiled using the Master Levels and included a demo lump for NESSUS. If I let the demo play normally as part of the Doom Loop, it goes out of sync. If I play the demo using -playdemo, it plays IN sync. If I have that demo as demo2 with another demo as demo1, the NESSUS demo is IN sync within Doom Loop too, but the other demo is... You get my drift.
This same scenario also goes out of sync with Chocolate Doom but IN sync with PrBoom.

I think it's more a question of timing.

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kb1 said:
Because of the implementation of the revenant tracer code (and maybe other places, can't remember now), and it's dependence on gametic, your demos must be started at the proper gametic. That's why -playdemo works, but it fails in the demo loop. TITLEPIC timing is also an area to check, because it also affects gametic, as does the pause key. Boom was the first codebase to attempt to address these things. Look for 'basegametic' (SP?) in Boom source to see how to begin to solve these tricky issues.

Basically, the fix involves "tricking" the game engine, so it believes that each demo is starting at the proper gametic (170 tics for Doom titlepic, 385 for Doom II).

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fawtytoo said:


The pagetic for TITLEPIC (Doom II) shows as TICRATE * 11 (35 * 11 = 385). After some trial and error TICRATE * 9 makes my Master Level demo run in sync perfectly (TICRATE * 1 also works).

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kb1 said:
Heh, try (TICRATE * 9) - 4 and see if that stays in sync too.

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fawtytoo said:

In fact, the only ones that work are 1, 5, 9, 13, & 17. There is a definite pattern there.

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fraggle said:
If you want to do demo playback testing, you might want to look at statcheck, the automated testing system I wrote for Chocolate Doom that uses statdump.exe to compare the statistics output to the behavior from Vanilla Doom.

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chungy said:
It's not a Windows program, it's a DOS one intended to be used in conjunction with vanilla Doom. You can run it inside DOSBox.

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fawtytoo said:
In the code, Plutonia & TNT are only referred to twice: for map name strings & title name strings. Are there any differences between Doom2 and Final Doom in the game engine?

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_bruce_ said:


Except for Lost Soul bounciness it quasi identical as far as I "know".

p.s.: forgot about the teleport behavior being different.

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