[0.4.0][Duke3D: DC] Player moves backwards when sliding wall

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Cacodemon345
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[0.4.0][Duke3D: DC] Player moves backwards when sliding wall

Post by Cacodemon345 »

When you slide along this wall in the 2nd map of Duke3D: DC, the player's up/down controls will be reversed. Not sure if this is a bug in the original.
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Graf Zahl
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Re: [0.4.0][Duke3D: DC] Player moves backwards when sliding

Post by Graf Zahl »

Build's movement code is notorious for its broken-ness. EDuke made some changes but it's doubtful they fixed everything. This sounds like an overflow resulting in a flipped sign somewhere.
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Re: [0.4.0][Duke3D: DC] Player moves backwards when sliding

Post by sinisterseed »

This is specific to that map and the surroundings of the main building as far as I'm aware, I experienced this myself as well but I think this is by design. Coming back on the sides after going behind the building doesn't seem to exhibit this behavior.

I know, one helluva nonsense but no idea what to make of this.
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Re: [0.4.0][Duke3D: DC] Player moves backwards when sliding

Post by Gammli »

Known eduke32 bug, started between r7824 and r7829:
https://forums.duke4.net/topic/10673-to ... l-service/
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Re: [0.4.0][Duke3D: DC] Player moves backwards when sliding

Post by Graf Zahl »

I was able to find out what particular change causes this, but even more interesting is that this code never worked right, it must seriously miscalculate something. The recently added overflow fixes now severely amplify that original problem.

Sadly I have no idea what kind of voodoo this function performs that makes it fail. For now I essentially reverted the offending part of commit 7829, but this is no real fix, of course.
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Re: [0.4.0][Duke3D: DC] Player moves backwards when sliding

Post by sinisterseed »

Never worked right? Hm.

Was this actually something that EDuke introduced or does it date all the way back to the OG DOS version/vanilla?
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Re: [0.4.0][Duke3D: DC] Player moves backwards when sliding

Post by Graf Zahl »

It even glitches when running under the most conservative compatibility mode which clearly hints at something very old. You can test yourself, if you slide against the wall and then turn closer toward it you wll already start backward. And when running in the opposite directrion you'll be faster.
The sliding math is as fucked up as Doom's - just differently.
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Re: [0.4.0][Duke3D: DC] Player moves backwards when sliding

Post by Rachael »

lowskill. wrote: Was this actually something that EDuke introduced or does it date all the way back to the OG DOS version/vanilla?
No, I remember this going all the way back to Duke Nukem 1.3D in DOS (I never had Atomic Edition until the middle of last decade).

I used to map for Duke quite a lot, mostly a lot of experiments because I was fascinated by the Build engine at the time. And I discovered this glitch back in those days.
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Re: [0.4.0][Duke3D: DC] Player moves backwards when sliding

Post by sinisterseed »

Fascinating, so it's a vanilla bug after all.

I didn't manage to cross check this yet in Megaton too (since I have that, why the hell not, even if it isn't of much use in this case), but if it's that ancient I'm reasonably confident it's broken there too.
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Re: [0.4.0][Duke3D: DC] Player moves backwards when sliding

Post by Graf Zahl »

If the bug is present on Nuke.YKT's demo-compatibility for Blood, RR and Exhumed you can be rest assured that this has been there since the inception of the Build engine. It's just a flawed algorithm that has always been flawed.

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