Slop Pack - Ideas and proof of concepts

[TRPB]

https://github.com/TRPB/dethrace-slop-pack

Thanks for the great project. I've been playing Carmageddon since 1997 (The very tail end of it) and every couple of years I fire it up, get frustrated that my 3dfx performance is somehow worse than I had 25 years ago, play a few races and give up. Dethrace is amazing, it's totally brought back my inner 12 year old.

This fork is entirely AI but I had some fun exploring what might be technically possible and what's fun. The benefit of AI is that you can prototype stuff really quickly and see what works and what doesn't. Code quality is generally poor since it's AI so not going to create PRs, it's just for fun (Hey, it's a game!)

In addition to simple quality of life stuff (Widescreen, MSAA, custom resolution). I fixed some bugs and added some fun features.

Achievements

During race:

Menu that allows you to scroll through them:

I had some fun with the achievement names:
https://github.com/TRPB/dethrace-slop-pack/blob/df920552b3b1443afe65869ba2ee72e39e465449/src/DETHRACE/common/achievements.c#L31

Dynamic Meld + Arena tracks

By specifying Meld=1 in config it dynamically melds all the games listed in [Games], you point it to the CARMA, CARSPLAT and XMASDEMO directories and it melds them, deduplicating opponents and having the option of starting with both your character's starting cars e.g. max gets Eagle I and Eagle II.

You even get the Splat Pack/XMAS Demo loading screens on those games. Implementation wise this uses a virtual file system where it scans files in all directories and merges opponent lists, races.txt, etc.

While I don't think this AI implementation should be considerd for upstream. This is definitely the way to go for melding in future and the virtual file system approach is probably the right option

Meld arena tracks

Adds Arena tracks SUMO and COLISEUM into the single player campaign, gives the opponents multiplayer

Meld other player car

If you're playing as Max you can have Die Anna as an opponent, if you're playing as Die Anna you get Max as an opponent

Bug fix - Camera judder

When you drive up hill the camera heaves significantly, I got AI to add some proper camera stabilisation to prevent it. The physics remain unchanged

This has frustrated me since about 2003 when I had a computer that could run the game fast enough to notice it. I remember playing with dgVoodoo back in the mid 2000s and spent ages messing with timing and other stuff trying to fix it. Finally fixed!

Bug fix - Pedestrian spasm

That's what I call it anyway. It's been in the game since 1997 and irked me since then. Peds sometimes swap between two different states between frames so they look like they're moving insanely fast

Quality of life

I wondered why the cutscenes weren't playing on my Steam copy. Steam ships a GAME.GOG/SPLAT.GOG cd ISO image. This fork loads the ISO and plays the cutscenes from there. Otherwise for Dethrace you need to manually mount the ISO or extract the cutscenes into the CUTSCENES dir

(This one of those labourious tasks nobody really wants to do and AI is great for)

I'm still having some fun adding features/fun things. I have a WIP multiplayer relay server but that's it's own project.

[dethrace-labs]

nice, love the work!

For "Bug fix - Camera judder", we have the setting PhysicsPerFrame in the ini file (under General) or --physics-per-frame arg. This might be the same/similar fix to what you have?

[TRPB]

Yeah, PhysicsPerFrame definietly helps but it doesn't fix camera heav on ramps. The easiest test is driving straight up the first hill in Maim Street using the Eagle. Look at the top of the buildings to see the camera have.

The issue is that at speed the car's suspension causes the car to bounce, because PointCameraAtCar compuptes directly from the car's direction the suspension causes an oscilation where the camera jumps up and down.

Here's a video of the problem, slowed down to 30%. It's actually more noticable than the video even makes it look, I recorded 144fps gameplay and obs limits to 60fps.

https://www.youtube.com/watch?v=aL3oWMXsjxc

1st half is with PhysicsPerframe=1 2nd half is with PhysicsPerFrame=1 and CameraJudderFix=1. You can see I wasn't able to eliminate it entirely but it's significantly less jarring in game.

There's two different parts to the fix:

1. PointCameraAtCar. The original code uses the raw position to calculate the angle: BrMatrix34PreRotateX(m2, theta - BrRadianToAngle(atan2(m2->m[3][1] - pos->v[1], dist))); because the camera is rigidly computed from the car direction any suspension bump is included and you get the juddering/camera heave while going up hill. By calculating the camera Y position based on the previous frame some smoothing can be applied and the judder removed.

2. But that's only half of the problem. I was quite happy when finding a fix for that, but then realised that even with the scenery now visually stable the car itself teleports slightly in position. That's not the camera, the rendered mesh for the car itself has the same problem. I did the same thing in InterpolateCars but actually that does feed back into the physics so I need to revist that :( It's a very subtle nudge to stop the oscillation but I was trying to avoid changing the physics itself

[dethrace-labs]

for Bug fix - Pedestrian spasm - when do you see this? The case I've noticed (but seems to only happen in dethrace or at least be much worse) is when slowly approaching a ped, and the ped is at the end of their path so they have nowhere to run to next, thats when there is an ugly flicker between standing and alarmed (normally hands raised). But so far I've put this down to a dethrace (or possibly just high framerate) bug, that I dont really see in vanilla carm95

[TRPB]

It's definitely a pre-existing bug. It's something I remember seeing as a kid playing the game. Here's a video that shows it happening on carma rather than dethrace: https://youtu.be/iv0VoXgwE88?t=587 or https://youtu.be/o1Trvy_DF6A?t=13

It's definitely less noticable at lower framerates. There's likely a better fix than the one in my branch, some kind of higher level "Don't revert to action that was N-1".

I used claude and a lot of trial/error with debug logs to track it down. The biggest culprit is MungePedestrianPath, if a ped can't find a path due to something blocking (wall, object, edge, etc) it triggers the panic action, then tries to find a path, then triggers panic, in a loop. There's also some floating point issues in MungePedestrianSequence where the angle flips between 0 and 360 degrees causing different

[sergcrack]

Hello, I really liked your work on improving Carma. Could you please upload the finished build to moddb.com? Here’s the section: https://www.moddb.com/games/carmageddon