In practice, if x1 is actually a collection of points (i.e. a 3d mesh) is the motion / physics of the spring mass calculated for each point in the mesh individually or is it calculated once for a focal point in the mesh (e.g. the center of the mesh) and then applied in a similar manner to each point within the mesh?
What are some common, non-obvious uses of springs in graphics/games? Isn't the possibility of oscillation/instability in numerical integration environments always a risk?