Driving Car System

Driving Car System is a two-mode interactive driving tool I built in Unreal Engine Blueprints at Versatile Media in 2022. It supports two ways of capturing a vehicle scene on the MoCap volume: actor-driven mode, where a button-triggered attachment system locks every MoCap actor, prop, and virtual camera registered as “inside the car” to the car as a single rigid unit while the actor drives; and operator-driven mode, where an operator drives the virtual car with a keyboard while the actor performs in front of a projection-mapped environment, reacting live to the drive.

The same custom car physics Blueprint, attachment system, and projection mapping integration drive both modes. Switching between them is a matter of which input source is connected at the time, not a different rig.

In short: one car, two ways to drive it, depending on what the shot needs.

The problem

Capturing a vehicle scene on a MoCap volume usually means picking one of two compromises. Either the actor drives the car themselves in MoCap, with everything attached so it moves together, but then the path through the environment has to be authored live and isn’t repeatable; or the team pre-keys the flight path and MoCaps the actor reacting against it, but then the path looks like 3D-on-rails and the actor has to act against motion they can’t actually see.

A single tool that supports both modes lets the production pick whichever mode each shot needs without rebuilding the rig.

What it does

Stable custom car physics. A Blueprint built from scratch so the car drives, brakes, and stops cleanly. No jump, no vibration, full-stop on demand. The foundation every other feature in the tool sits on.

Actor-driven mode (button-triggered attachment). A single button press attaches every MoCap actor, prop, and virtual camera registered as “inside the car” to the car as a single rigid group. The actor “drives,” everything riding with them moves together, the camera follows naturally. A second press detaches everything cleanly so the actor can step out and into the next moment without leftover offsets or floating props.

Operator-driven mode (keyboard drive). WASD on an operator’s keyboard maps to the same throttle/brake/steer inputs the actor’s MoCap-driven controls feed. The car can’t tell which mode it’s in; it’s the same control surface either way. Lets an operator drive the virtual car while the actor performs in front of the projection-mapped environment, reacting live to the drive.

Projection mapping integration. The car’s position and orientation in Unreal feed the studio’s projection mapping pipeline, so what’s projected on the volume around the actor stays in sync with the virtual car’s drive. The actor sees the world moving the way it would actually move from inside a moving car.

Technical implementation

Built in Unreal Engine using Blueprints. The custom car physics replaces standard vehicle assets with a tuned damping model that removes vibration, an explicit full-stop logic for clean deceleration, and drive/reverse responsiveness suited to performance capture pacing rather than racing.

The attachment system registers MoCap actors, props, and virtual cameras as “attachables” on the car. On button-press, the system parents all registered objects to the car’s transform; another press unparents them and restores their independent positions. Pure transform parenting means a knock to the car translates straight through to the riding components, same as a real car.

The keyboard input layer maps WASD to the same throttle/brake/steer Blueprint inputs the MoCap-driven controls feed in actor-driven mode. The car can’t tell whether it’s being driven by the actor or the operator; the input source is interchangeable.

The projection mapping integration feeds the car’s position and orientation into the studio’s two-projector floor mapping pipeline, so the world projected around the actor in the volume matches where the virtual car is in the scene.

Origins

Before the Driving Car System existed, Versatile Media’s most recent vehicle project was Wasteland (September 2022): a desert car race built on Unreal Engine’s stock Chaos vehicle physics. The Wasteland team was Raphael Gaudin, Mohammed Badah, Evan O’Reilly, Kyle Liu, Shouyu Yang, Yuan Zhang, and Isabella Hallam. I wasn’t deeply involved on Wasteland itself, but the project served as the studio’s working reference for what realtime vehicle work in the volume looked like.

When Scavenger came along right after, I took on building a new car driving tool from scratch, using Wasteland’s setup as the starting base. The Driving Car System replaces Chaos with custom Blueprint physics tuned for performance capture (no jump, no vibration, full-stop on demand), adds the dual actor-driven and operator-driven modes, and integrates with the studio’s projection mapping pipeline. The general goal is the same as Wasteland (drive a virtual car in the volume), but the new tool was built around the repeatability and direct-control flexibility a MoCap shoot actually needs.

In production

Built for and used on the Scavenger demo at Versatile Media in 2022. Both modes shipped with the demo. The tool is reusable: the core architecture (custom physics + attachment system + keyboard fallback + projection mapping integration) generalizes to any vehicle scene that needs both pilot and react coverage. New vehicle, swap the physics; same attachment, same keyboard layer, same projection pipe.