Sul Sul, Simmers,
After receiving community feedback, we’re excited to be releasing some significant improvements to eyelid functionality in The Sims 4 with the free Base Game update on March 17th. This wasn’t a single fix, and it required many teams across QV, Tech Art, Animation, and Create a Sim working together to trace the issue across assets, systems, and workflows. This type of work is normally hidden to the average player, so we wanted to share a breakdown of the work that went into making this improvement possible.
We hope you find it interesting, and for mod authors, useful!
Eye See What You Did There
Before any work could get started, the QA team first looked into player reports, verified what was happening in the game, and created detailed replication steps. This included where blinking was being limited, where it was being exaggerated, and how eye shape variations complicated both. That information was then passed on to the Tech Art team.
Good Eyedea to Adjust Animation in Maya Files
A Tech Art script scanned all Maya files in The Sims 4 Base Game and DLCs to identify upper eyelid rotation animations. It targeted those within a specific range: enough to detect eyelids not fully closing but not detect intentional poses like squinting. The script then adjusted these animations, either increasing or decreasing the eyelid rotation to match the value required for eyes to fully close. If the rotation already exceeded the closed-eye threshold, the script reduced it appropriately. This process fixed a great number of eye blinking issues where the eyelid rotation either too high or too low in the default Sim mesh animators use in Maya.
What remains: While a great deal of eye blinking issues in Maya has now fixed, this does not automatically resolve all Sims character blinking in the Create a Sim system. Each eye shape archetype in Create a Sim requires a different rotation amount to fully shut the eyelids. Previously, rotation was dampened globally to avoid eyelash clashing, especially after the addition of new lower eyelash assets in The Sims 4: Lovestruck.
These Are Getting Cornea
Each eye shape preset in Create a Sim has unique joint values, shaping the eyes into various archetypes. To ensure eyes close correctly for every eye shape, a specific rotation multiplier is applied to each preset. Earlier, eyelid rotation was globally dampened to prevent over-blinking due to lower eyelash geometry. However, this sometimes led to under-blinking. The new approach finds an ideal balance, further reducing under-blinking without causing excessive over-blinking.
Iris There Was More
For interactions highlighted by players as problematic, the Animation team manually refined over 280 animation files (list below) to ensure eyes fully close without any eyelash clashing. The “half-blink” in Create a Sim, originally an intentional animation style, was changed to a complete blink to avoid confusion with actual under-blinking. Mood-based sleep loop animations were also improved for smoother transitions. Facial overlays were removed to prevent double-layered facial expressions during these loops. A Create a Sim artist has reskinned the lower eyelashes, allowing them to move more accurately with the lower eyelid.
Eye’ve Heard Enough, Let’s Put a Lid on This
In rare cases, some unique eye shapes may still display slight over-blinking. This was considered preferable to widespread under-blinking. Player-created poses and animations were not individually adjusted but will still benefit from the global Tech Art script and modifier updates. Player-created Sims will see improvements from these global fixes, though some unique eye shapes may still show minor blinking inconsistencies.
As with any systemic fix, we’ll be closely monitoring for additional issues after release.
List of fixed animation files attached below
The Sims Team