What does PhysX do?

“A few of my games have an option called “PhysX” in video settings.

“A few of my games have an option called “PhysX” in video settings. I know this is supposed to makes games look better, but what exactly does it do, and why do only some games have it?” – Charles F.

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PhysX is an Nvidia-based API designed to provide a standard, GPU accelerated way of modelling realistic object dynamics in 3D environments. Why use a boutique graphics card instead of a beefy CPU? It turns out that the highly parallel structures used by GPUs are particularly efficient at processing complex physical simulations. Think Batman’s cape, Geralt’s hair or the musket flash and smoke in Assassin’s Creed: Black Flag. Mirror's Edgewas one of the first showpiece games for PhysX cloth physics.

The result is a flashy, next-generation experience that’s nice to have in your games, but PhysX comes with a few drawbacks.

The Arkham series has supported PhysX since Asylum. PhysX is turned off on the left.

While the API is technically available to all, only Nvidia hardware is optimized for use with PhysX. This makes plenty of sense for Nvidia, but locks you to team green, so it’s worth keeping in mind for AMD fans. Moreover, not just any Nvidia card will do. Like any other graphics card feature, you’ll need to cut a healthy check if you want to turn the settings up all the way. First class seats (read: great performance, even with all the bells and whistles on) require 980-level hardware. Even in the virtual world, cool hair and slick threads don’t come cheap.

Witcher 3 makes extensive use of PhysX along with the rest of NVidia’s Gameworks enhancements.

Also, since PhysX is a separate API it requires explicit support from software developers written into the code. This extra effort means many programming teams don’t bother so support is hit and miss. The best implementations frequently rely on Nvidia’s assistance during development.

Even with support present, a lack of optimization can produce large FPS drops or uneven performance. As a result, the library of games that support PhysX weighs in at around 40, surprisingly low given how long PhyX has been around. While there are some carefully selected blockbusters in that modest number, it’s just a drop in the Steam backlog bucket for most serious gamers.

One fix for SLI users experiencing uneven performance is dedicating the secondary card to PhysX requests.

That said, when properly used, the difference PhysX provides is dramatic. Smoke is richer, thicker, and more volumetric. Fabrics ripple realistically in the wind, and glowing particles crackle from flames and gunfire. It’s a visual upgrade you can appreciate without freeze-frames or Photoshop analysis. Demos give an even better look, with optimized code that pushes the API’s advantages to the limit, a glimpse of what universal support might have looked like.

Borderlands 2 comparison shot, PhysX is turned off on the left.

However, with developer interest cooling in favor of newer technologies PhysX is best considered a handy plus for Nvidia aficionados rather than a current, must-have feature. If you’re looking for a reason to spend a few extra hundred dollars on a rig for visual upgrades or cutting edge excitement, you’ll be better served investing in a 144Hz IPS gaming monitor or nice VR headset.

Additional Resources
PhysXInfo.com