RFactor

ISI had been developing commercial and military simulators since the early 1990s. The isiMotor2 engine powering rFactor was a direct successor to the engine used in F1 Challenge '99–'02, ISI's earlier collaboration with EA Sports. Unlike that title, rFactor launched without licensed Formula One circuits or teams; the initial release contained four fictitious circuits with roughly seven layouts across those facilities and approximately six vehicle classes, including two open-wheel and four sedan categories. Dropping real-world licenses also meant the game was published without EA Sports, ISI's longtime partner.

A central design priority was the modding interface. The game shipped with rich tools for creating custom vehicles and tracks, which allowed amateur developers to expand the content library far beyond what ISI delivered at launch.

rFactor's tire model was conceived as an improvement on the Pacejka model widely used in earlier simulators. It simulated a non-linear use cycle governed by temperature and wear, attracting notable early praise from the sim-racing press. Early preview coverage noted the model's superior handling of the relationship between slip angle, self-aligning torque, and cornering force.

A major full update arrived in August 2006, introducing the 2006 BMW Sauber F1 car, a comprehensive manual, and driver-swapping functionality. Driver swapping enabled teams to change drivers mid-race, making events of up to 24 hours — such as a simulated Le Mans — possible within the game. Version 1.250 followed in January 2007, and a patch in October of the same year brought the release to version 1.255 build F.

The AI system gained a "track learning" feature that trained computer-controlled opponents to find more optimal lines around a given circuit. By version 1.150, improved AI produced noticeably faster driving styles.

Multiplayer was facilitated through ISI's own central server infrastructure, which listed all active races and practice sessions through a web interface called Racecast. Registered drivers could maintain career statistics. A dedicated server program allowed online sessions to run without a graphics renderer, reducing hardware requirements for hosting. The game also offered a plugin interface for third-party add-ons, enabling features such as screen overlays and radio chatter.

Circuits within rFactor were structured to include all layouts available at a given real or fictional facility within a single track package, eliminating the need to duplicate geometry across multiple files.

rFactor was nominated as a finalist for PC Gamer US's Best Racing Game of 2005, an award that ultimately went to GTR: FIA GT Racing. Critical opinion recognized its simulation depth while noting that accessibility limitations made it unsuitable for players who did not specifically demand realistic simulation behavior.

ISI developed a sequel, rFactor 2, released on March 28, 2013. The successor introduced dynamic weather effects, accurate shadow rendering across varied surface textures, and visual reflections. It also incorporated Real Road technology, which simulates the gradual laying of rubber on the track surface to alter grip levels in real time over the course of a session. The thermomechanical tire model in rFactor 2 extended the original's approach to include flatspots and carcass deformation. Studio 397 later took over development of rFactor 2 after ISI wound down its consumer software activities, and Motorsport Games subsequently acquired Studio 397 in 2021.

The isiMotor2 engine found application beyond the rFactor consumer titles, underpinning rFpro, a professional driver-in-the-loop simulation tool used by racing teams for vehicle development and driver training. The broad modding community that rFactor cultivated produced hundreds of vehicles and circuits and established workflows that influenced how sim-racing content creation was organized across the genre for years afterward.