Recent 1.3 Beta update (availabe through Steam on PC) for Fallout 4, among various bug fixes, adds several new graphics features – HBAO+ ambient occlusion and, suprisingly, physically simulated debris effects from bullet impacts, exclusive to NVIDIA GPUs.
We can’t say that debris effects in Fallout 4 are that spectacular, as they suffer from standart shortcomings of PhysX-style content added post-release – static game world with mostly non-destructible objects and exsessive amounts of particles have some problems mixing in. For example, shooting a small object (such as a chair) can produce more debris than the volume of the object itself.
However, if one look closer at the technical aspects of FLEX based debris implementation, they can notice very nice and promising details.
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 importanly, debris can’t interact with each other.
As you may see on the following screenshoot from Borderlands 2, rock debris are clipping into each other, forming a flat “puddle” on the ground.
FLEX solver, in comparison, support interactions between individual particles or particle groups. That results in much more natural and dynamic behaviour – in Fallout 4, debris can even form a “volumetric” pile, thus acting like a real rigid bodies, not simple particles (shadows are yet missing, yes).
So, long awaited GPU Rigid bodies have arrived in a form of a FLEX debris. We are curios to see how the technology will evolve in the future titles.