Fake Physics With Dynamics
When people say they want physics in an animation tool, they usually do not mean a rolling-boulder simulator. They mean the little truths that sell weight: hair that lags, a belly that jiggles, a tail that keeps swinging after the body stops. FoundryInk has no whole-scene physics engine, so this page says so plainly, and then teaches the thing you actually reach for, Dynamic bones, in full. Rig the loose parts, tick one box, tune three dials, and secondary motion happens for free.
1What people mean by physics
In character work, physics almost never means simulating gravity and collisions across a whole scene. It means the small automatic wobble that makes a body feel like it has weight: follow-through on hair and cloth, overlap where a hand trails the arm, and the settle where a bounced thing comes to rest. Those are the details a viewer cannot name but instantly misses when they are gone. You can produce all of them from your rig, no simulator required.
2No whole-scene physics
The plain fact, so you never hunt for a button that is not there: FoundryInk has no whole-scene physics. There is no gravity setting, no rigid-body collisions, no cloth solver that reacts to a floor. If a book must tumble down real stairs and bounce off each step, you animate that by hand, frame by frame or with keyed poses. Do not go looking for a Physics panel, because there is not one, and knowing that saves you an afternoon.
3The real substitute: Dynamic bones
The substitute is per-bone springiness, and it covers the vast majority of what people wanted physics for. In the Bones panel, tick Dynamic on a bone and it stops following its parent rigidly, it lags behind and springs back like a thing on a soft spring. Three dials shape that spring: Stif for stiffness, Damp for how fast the wobble dies, and Inert for how much it overshoots. That single checkbox is the heart of every bounce and jiggle in this tutorial.
4Map physics jobs to dynamics
It helps to see exactly which physics wishes Dynamic bones grant. Follow-through, where hair keeps moving after the head stops, is a Dynamic chain. Overlap, where a hand lags the arm, is a Dynamic bone at the end of a limb. Jiggle, for a belly or jowls or a soft prop, is a Dynamic bone buried in the soft part. Settle, where a bounced antenna wobbles to rest, is Dynamic with low damping. Sway, like grass or a scarf in a breeze, is Dynamic reacting to any scene motion. That is most of the physics wishlist, right there.
5Rig the loose bits with bones first
A Dynamic bone can only wobble the art bound to it, so before anything springs you need bones in the floppy parts. In Rig mode, pick Add Bone and drag a small chain down each loose bit: two or three bones along a ponytail, one at the tip of an ear, a short chain through a scarf. Select the parent bone first so each new bone chains off it, and bind the soft art to those bones with Bind to bone or Flexi Bind for a bendy shape. No bone in the floppy part means nothing to make Dynamic.
6Tick Dynamic
Select a bone in your loose chain and, in the Bones panel, tick Dynamic. The moment it is on, that bone no longer rigidly obeys its parent, it trails and springs. Tick it on every bone in the floppy chain, not just the first, so the whole tail or scarf ripples rather than swinging as one stiff plank. The defaults give you a reasonable wobble straight away, which you will then dial in to taste.
7Stif: how hard it snaps back
Stif is stiffness, how strongly the spring pulls the bone back toward its rest angle. Turn Stif up and the bone feels tight and wiry, snapping back quickly like stiff wire or a firm quiff of hair. Turn it down and the bone feels loose and heavy, drooping and swinging lazily like a wet rope or a long tail. Match Stif to the material you are imagining: springy for a bouncy antenna, slack for heavy braids.
8Damp: how fast the wobble dies
Damp is damping, how quickly the wobbling energy bleeds away and the bone comes to rest. High Damp settles almost at once, one small sway and it is still, which suits something moving through thick air or heavy cloth. Low Damp lets the wobble ring on and on, sway after sway slowly shrinking, which suits light springy things like a thin antenna or a loose spring. Damp is your control over how long the party lasts after the motion stops.
9Inert: how much it overshoots
Inert is inertia, how much the bone overshoots its target before swinging back, the source of that satisfying whip and bounce. High Inert throws the bone well past where it is heading, giving a big loose flick before it recovers, great for a heavy swishy tail. Low Inert keeps it tight, barely overshooting, which reads as light and controlled. Inert is where the drama lives, so it is the dial to reach for when a wobble feels flat.
10Ignore wind, and the wind that is not there
Under the Dynamic settings sits a checkbox, Ignore wind. Leave it unticked and the bone reacts to scene motion, so it sways when the character moves and stays part of the action. Tick it and the bone ignores that ambient push, useful when one part should stay calm while everything else sways. Note there is no scene-wide wind panel to set a global breeze, the only wind control is this per-bone toggle. Your sway comes from Dynamic bones reacting to motion, not from a wind dial.
11Tune the feel in Test mode
You cannot judge a spring by staring at it, you have to shake it. Switch the banner to Test mode, where you can drag bones to preview and nothing is saved, then give the character a firm sling side to side and watch how the loose bits react. Tweak Stif, Damp, and Inert, shake again, repeat until the wobble feels right. Because Test mode saves nothing, you can flail your puppet around with total freedom while you find the sweet spot.
12A bounce and jiggle recipe
For a soft jiggle, a belly, cheeks, a plush prop, bury a Dynamic bone in the squishy area and bind the soft art to it with Flexi Bind so the wobble spreads smoothly. Keep Stif low for that heavy jelly feel, Inert moderate so it overshoots and settles, and Damp mid so it bounces a couple of times before resting. Now animate the body landing from a jump with your keyed poses, and the belly bounces on impact all by itself. You never keyed the jiggle, the spring did.
13Follow-through and settle
Follow-through is the payoff you set up for: the character stops, but the Dynamic hair, cloth, and tails keep going a beat, then settle to rest. To get a clean settle, raise Damp a little so the wobble does not ring on past the moment, and keep Stif true to the material so it returns to the right resting shape. Hold on the last pose for a few frames and let the springs finish, that final settle is what makes an ending feel deliberate rather than abruptly cut.
14What good looks like, and the real gaps
Good dynamics are felt, not noticed: the tail swings with the walk, the belly settles after a landing, the scarf drifts a half-beat behind. If a wobble is jarring, you have overcooked Inert or starved Damp, so ease back until it reads as natural. And keep the real gaps in mind, there is no collision, so springs pass through floors and props, and there is no gravity or scene physics, so real falling and tumbling is hand-keyed. Everything else on this page is live and does the job.
Dynamics questions
No. FoundryInk has no whole-scene physics, no gravity setting, and no rigid-body collisions. For real falling, tumbling, or objects bumping and stopping each other, you animate that by hand with keyframes. For soft secondary motion like bounce and sway, use per-bone Dynamic springs.
Add a short bone chain down the tail in Rig mode and bind the art to it. Select each bone and tick Dynamic in the Bones panel, then tune Stif, Damp, and Inert. As the body moves, the Dynamic bones lag and spring, so the tail swings without you keying it.
Stif is stiffness, how hard the spring snaps back (high is wiry, low is floppy). Damp is how fast the wobble dies (high settles quickly, low rings on). Inert is how much the bone overshoots before returning, which gives the whip and bounce. Change one at a time so you learn each dial.
Your Damp is too low, so the wobble never bleeds off. Nudge Damp up until the tail settles in a believable beat or two. If it also feels too whippy, ease Inert down at the same time.
Correct, there is no scene-wide wind, only the per-bone Ignore wind toggle. Leave Ignore wind unticked so the bone reacts to motion, then give the character a tiny bit of keyed body sway. The Dynamic scarf sways in response, and that gentle motion reads as a breeze.
Tick Ignore wind on a bone when it should stay calm while the rest of the character sways, for example a stiff prop held in a hand that should not wobble with the body. Left unticked, the bone joins the ambient motion. It is a per-bone opt-out, not a global wind control.
No, there is no contact detection. A Dynamic bone will swing straight through a floor or prop if your keyed motion sends it there. For anything that must hit and react to a surface, animate the contact by hand.
Yes, that is the point. You animate the primary motion with keyed poses, and the Dynamic bones add the lag, overshoot, and settle on top automatically. Preview and tune the feel in Test mode, where you can drag the puppet freely and nothing is saved.
Weight, without the maths
No physics engine needed. You rigged the loose bits, ticked Dynamic, and tuned Stif, Damp, and Inert until hair lagged, bellies jiggled, and tails settled all on their own. That is the secondary motion that gives a character weight. Next, learn to automate the app the native way, no scripting required.