Standard gravity in units/s², as a signed Y component.
Appendix A pins gravity at (0, -9.81, 0) m/s² in a 3D world and
(0, -9.81) in a 2D one — the same vector, because §7a puts +Y up in both.
Used by @fourjs/physics as the default world gravity and by
@fourjs/particles as the default acceleration of uniformGravityField.
Standard gravity in units/s², as a signed Y component.
Appendix A pins gravity at
(0, -9.81, 0)m/s² in a 3D world and(0, -9.81)in a 2D one — the same vector, because §7a puts +Y up in both. Used by@fourjs/physicsas the default world gravity and by@fourjs/particlesas the default acceleration ofuniformGravityField.