Recent update for Fallout 4, 1.3 Beta update (available through Steam on PC), next to various bug fixes, adds several new graphic features including – HBAO+ ambient occlusion and, surprisingly, physically simulated debris effects from bullet impacts, exclusive to NVIDIA GPUs. The new debris effects are surprisingly not based and are not using any portions of PhysX SDK, like many other GPU PhysX games, but completely based on the new NVIDIA FLEX solver. PhysX FleX (NVIDIA FleX) is the new GPU accelerated particle-based physics simulation library. The core idea of FleX is that every object is represented as a system of particles connected by constraints. Such unified representation allows efficient modeling of many different materials and natural interaction between elements of different types, for example, two-way coupling between rigid bodies and fluids, or fluids and soft bodies. Because FleX is not designed to build gameplay affecting physics, It is recommended to use FleX in conjunction with a traditional rigid-body physics engine, such as PhysX SDK (PhysX SDK 3.4 will feature native FleX integration).
The debris effects in Fallout 4 are not that spectacular as someone could think mainly because they suffer from standard shortcomings of PhysX-style content added post-release – static game world with mostly non-destructible objects and excessive amounts of particles have some problems mixing in. One nice example, shooting a small object (such as a chair) can produce more debris than the volume of the object itself. This is quite, ehm, strange. However, the technical aspects of FLEX based debris implementation are very promising and we can wait evolving of this technology in the future.
Particle debris for weapon effects are commonly used in GPU PhysX games, such as Alice: Madness Returns, Borderlands 2, Batman: Arkham City, Metro: Last Light, etc. Usually, a debris is represented by 3d mesh object (that can be fairly complex) in the graphical world and by simple dot-like particle object in the physics engine scene. Such approach is the most performance effective, but affects the realism in the negative way – debris rotation and secondary motion are “semi-faked” (approximated), collision with static objects are simplified and, more importantly, debris can’t interact with each other.
Bottom line, FLEX solver, in comparison, support interactions between individual particles or particle groups. That result in much more natural and dynamic behavior – in Fallout 4, debris can even form a “volumetric” pile, thus acting like real rigid bodies, not simple particles (shadows are yet missing, yes).
More information at: physxinfo