Devlog 3: Next Fest and major demo updates

The Throttle Trace demo has been out for nearly 2 weeks! Ahead of Next Fest, I've prepared a whole swath of new features. Where do I even start?

Replay mode

Want to relive the glory of your last lap overtake for P1 over and over? Or get to the bottom of who exactly is responsible for that safety car? (It definitely wasn't you, no way. You're an angel.)

Now you can select "Replay" during or after a race to watch these moments play out to your heart's content.

Wheel-to-wheel overhaul

One of the early design questions for Throttle Trace was "how does wheel-to-wheel racing work in a game without steering?". My original approach was to divide the track laterally into 5 lanes (racing line, inside, outside, far inside, far outside), and automatically assign cars to one of those lanes from the AutoLane system. For about a year I've been iterating on that approach, obsessing over how to create natural driver behaviors. It wasn't a bad solution, but it had limits.

I found that the racing could look rigid and unnatural at times. I couldn't solve the tradeoff between lane changes looking abrupt versus cars clipping through each other if they don't change lanes fast enough. Collisions were a problem too: how can you straight-line a chicane? Or run wide into the barrier? If you're limited to 5 lanes, those behaviors are impossible to model well.

So I built a new offset-based system. I watched replay after replay, looking for unnatural behaviors to weed out. I made a dev tool that overlays the system's logs for a given driver during the replay, so I could precisely diagnose how the system's decisions were mapping to what I am seeing in the replay.

I spent several days iterating on this nonstop. Running a race, watching the replay, pausing every time I saw something that didn't look right, looking at the decision logs, updating the code, go again. I am genuinely proud of the result. It's not perfect (cars can sometimes awkwardly merge together at the edge of the track, or when getting sandwiched by two cars ahead), but it's a much more dynamic and authentic simulation.

Collisions

Send it!

Previously, the collision physics were... I mean, you could barely call them physics. It was a simply rule wherein, if the driver on the inside of a corner makes a mistake, an "incident" would be created for any driver to their outside. This worked for creating stakes when overtaking/defending. It also looked (here's that word again) unnatural.

The reason I resorted to this simplified system to begin with was the old lane system. It wasn't possible to have a purely physics-driven incident resolution and then "re-attach" the car to a lane, at least not in a way that looked reasonable. But with the new offset-based system, once a driver regains control, their offset is simply the distance between their current position and the nearest point on the racing line. The system takes it from there, and the car rejoins seamlessly.

Now, cars have proper collision bodies like any racing game would. When a car loses control, the physics engine will detect collisions with other cars and measure the velocity of impact, deflection angles, etc. These all feed into determining damage/penalty allocations.

Speaking of damage, look out for an update to the damage model in the future!

Fancy Trees!

Steam post image So fancy.

Adapted from this Godot foliage implementation. The Godot community is truly the best.

Chase Cam

I previously preferred the Isometric camera perspective, mostly because it papered over a lot of the quirks in the game's old lane system and collision handling. But with the work over the past several weeks, Throttle Trace is now ready for its close-up!

Well, maybe not entirely ready. Grandstands, pit lanes, buildings, track environments, these all still need a lot of attention. But the game does look dramatically better overall. Even if a chase cam perspective shows a few more warts, I think it holds up well and will only continue to improve.

What's Next

The immediate roadmap will shift as I gather feedback during Next Fest. The items that are top of mind (in no particular order)

• Driver avatars

• Updates to grandstands/pit lanes/building textures

• More track scenery

• Weather

• Damage and reliability model

The medium-term roadmap

• Co-op careers

• More career events and storylines

• Team economy simulation in career mode

• Play career as team principal or race engineer

There are a ton of things on the backlog as well, too many to list. Want to suggest a feature (or just come say hi)? Pop by the discord!