Is there any particular reason simulated physics in games usually feels so floaty/bouncy? Floppy ragdolls, swords sliding down hills, table settings prone to pop off the table, it just seems really difficult for physics in games to be made to feel right. What's up with that?
Mostly it’s because physics simulation is just an approximation, and that physical objects moving in reality have a whole lot more properties than the approximations can handle.
If you’ve ever taken a physics class in school, you must have noticed that the material tends to do things to simplify, such as assuming that the objects are in a vacuum, or that the velocity is applied instantaneously, and so on. These all serve to simplify the equations for the sake of teaching a principle. Real world physics are extremely complicated. There’s air resistance, friction, qualities of the materials that are involved, objects touching objects touching objects, and so forth and so on. There is also no cap on computing power for the real world to run at a high frame rate.
When a sword slides down a hill in a game, it’s because there’s some kind of gravity being applied to the object on an angled surface. Most game physics simulations just take basic properties into account like mass, various forces, and the (basic) properties of the material it’s on. We make approximations such that most visible things don’t behave super weirdly. Our physics simulation formulas are often incomplete - they work most of the time, but under the right conditions, for example, falling objects can steadily increase in their acceleration. This is why, in Skyrim (sometimes), objects falling and bouncing down a hill can get launched off into space - it’s because their physics simulation didn’t account for all of the factors at play in that situation.
Most of the issues stem from simplifications and assumptions we make to ensure that the physics simulation isn’t so complicated that it affects the frame rate. If you remember my old [Corpse Volcano story], there was always a noticeable performance hitch when I shot the bodies because there were suddenly dozens of physics objects (corpses) all exerting force on each other at the same time. I suspect that, as processing power improves, physics simulation will also continue to improve. We devs get more annoyed about the weird physics artifacts that we see than you do, because we are the ones who spend our time trying to make it look right to begin with.
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