Character Animation Starter Kit: Balance, Center of Gravity, and Ground Contact

1) Base of Support + Center of Gravity Projection

To make a character feel grounded, you don’t need advanced rigging knowledge—you need to manage where the character is supported and where their weight is going. The key idea: a pose looks stable when the character’s center of gravity (CoG) projects down to the ground inside the base of support.

Base of support (BoS): what counts as “support”

The base of support is the area on the ground that can hold the character up. In most shots, it’s defined by the parts of the feet that are actually in contact with the floor.

• Two feet down: the BoS is roughly the combined footprint area between and under both feet (think of it as a polygon around the outer edges of both feet).
• One foot down: the BoS shrinks to the contact area of that single foot (heel-to-toe if flat, or a smaller patch if on toe/heel).
• Partial contact: if the heel is lifted, the BoS is mostly the ball/toe area; if on heel, it’s mostly the heel area.

Projecting the CoG to the ground (simple animator method)

You rarely need an anatomically perfect CoG. Use a practical approximation: the CoG is usually near the pelvis/hips (slightly forward in many characters). To check stability, imagine a vertical line dropping from the hips to the ground.

• If that vertical line lands inside the BoS, the pose reads stable.
• If it lands on the edge, the pose reads precarious (useful for acting, but it will feel “about to tip”).
• If it lands outside, the character must be catching themselves (stepping, leaning on something, or falling) or the pose will feel floaty/unphysical.

2) Balance Rules: Two-Foot vs One-Foot Support

Two-foot support: stability is cheap, but weight still needs a “winner”

With two feet on the ground, the BoS is large, so stability is easy. The common mistake is that the character looks evenly supported when the pose implies otherwise. Even in a relaxed stance, one leg usually carries more weight.

• Rule: if the character is relaxed, pick a weight-bearing leg and a relaxed leg.
• Check: the hips should be slightly closer to (or above) the weight-bearing foot.
• Grounding cue: the weight-bearing side often looks “compressed” (hip slightly lower on that side, knee more loaded), while the free side looks lighter.

One-foot support: the CoG must commit over the planted foot

Standing on one foot is a strict test: the CoG projection must land within the planted foot’s contact area, or the character must counterbalance with a visible action (step, arm swing, torso tilt).

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• Rule: before lifting a foot, shift the hips so the CoG line drops into the planted foot.
• Rule: the torso can counter-tilt to keep the CoG over the foot (hips go one way, chest may go slightly the other).
• Rule: the planted foot should look like it’s taking load (ankle alignment and knee direction should feel supportive, not collapsing sideways unless that’s the intent).

Practical stability check: in a one-foot pose, if you hide the lifted leg, the remaining silhouette should still look like it could stand.

3) Planted Feet vs Sliding Feet: Locking Contacts and Maintaining Traction

“Floating” often comes from foot contact problems: the foot is supposed to be planted, but it drifts or rotates subtly. Your job is to decide, per foot, whether it is planted (locked) or traveling (sliding/stepping).

Decide foot state per phase

• Planted foot: stays fixed in world space (no translation), and usually no rotation unless pivoting on toe/heel intentionally.
• Traveling foot: moves across the ground (a slide) or lifts and relocates (a step).

How to lock a planted foot (without rigging tricks)

Even with a simple rig, you can keep traction by treating the planted foot as the anchor and moving the body around it.

1. Pick the planted foot and set its position/rotation first for the contact frames.

2. Keep that foot consistent across the contact range: same world position in front and side views (use your software’s motion trail/ghosting if available).

3. Move the hips/root instead to create the weight shift. If the character needs to lean, translate/rotate the hips and spine, not the planted foot.

4. Watch for “micro-slips”: tiny frame-to-frame drifts are very visible. If you see them, correct by matching the foot’s transform on the planted frames.

Common causes of unintentional sliding

• Hips moving too far without a compensating step: the body travels, but the foot is expected to stay planted—your rig/keys may drag it.
• Rotating the root while expecting the foot to stay fixed: root rotation often arcs the legs, pulling the foot.
• Changing contact type mid-plant: e.g., heel down to toe down without animating the pivot; it reads like slipping.

Intentional pivots (traction-friendly rotation)

If you want rotation while planted, choose a pivot point:

• Heel pivot: toe lifts slightly; rotation happens around heel contact.
• Toe pivot: heel lifts; rotation happens around ball/toe contact.

Animate the pivot clearly: show the heel/toe lift and keep the pivot point stable on the ground.

4) Using Hips/Root Control to Manage Weight Shifts

The hips/root control is your main tool for grounding because it represents the character’s mass. Think of it as moving the “bag of weight” over the support foot.

Two key moves: translate and tilt

• Translate (side-to-side): shifts weight from one foot to the other. This is the primary move for preparing a one-foot balance.
• Tilt (hip drop): adds the feeling of load. The weight-bearing side often drops slightly (subtle), while the free side rises.

Step-by-step: clean weight shift using hips/root

1. Start neutral with both feet planted and hips centered between them.

2. Shift hips toward the target support foot (translate). Keep both feet planted during this shift.

3. Add a small hip tilt to suggest load on the support leg. Keep it believable—too much becomes a stylized sway.

4. Counterbalance with torso if needed: if hips go right, the chest may drift slightly left to keep the CoG line over the foot, depending on the character’s proportions and stance width.

5. Only then lift the free foot. If the foot lifts before the hips commit, it reads like the character is weightless.

Quick diagnostic: “Which leg is holding the character up?”

Scrub the timeline and pause on any frame. Ask: if I removed one foot, would the remaining foot plausibly support the hips? If not, shift the hips/root until the CoG projection makes sense.

5) Practice: 4-Pose Balance Progression + Stability Checks (Front and Side Views)

This exercise builds a reliable grounding workflow you can reuse in walk cycles, turns, and acting beats. You will create four key poses: neutral stand, shift weight, lift foot, recover.

Setup

• Work in a simple scene with a visible ground plane.
• Use both front and side cameras (or split view).
• Decide which foot will become the support foot (example: left foot).

Pose 1 — Neutral stand (both feet planted)

1. Place both feet flat on the ground, about hip-width apart.

2. Set hips/root centered between the feet.

3. Check in front view: hips centered, knees not collapsing inward unless intended.

4. Check in side view: hips not drifting so far forward/back that the character would tip.

Stability check: CoG line from hips should land between the feet (inside the two-foot BoS).

Pose 2 — Shift weight (prepare for one-foot support)

1. Keep both feet planted and locked.

2. Translate hips/root toward the left foot until the CoG line drops into the left footprint area.

3. Add a subtle hip tilt to show the left leg taking load.

4. Let the right knee relax slightly (it can soften or bend a bit) to show it’s unloading.

Stability check: in front view, the hips should be clearly closer to the left foot; in side view, the hips should still project within the foot contact (not drifting forward/back).

Pose 3 — Lift foot (one-foot balance)

1. Maintain the left foot’s position and rotation (no sliding).

2. Lift the right foot cleanly: break contact by raising the heel/toe and then the whole foot.

3. Keep hips over the left foot; if the character wobbles, adjust torso/arms slightly for counterbalance rather than moving the planted foot.

Stability check: CoG line must land within the left foot’s contact area. If it doesn’t, either shift hips more or make the pose read as a near-fall (which requires a visible recovery step next).

Pose 4 — Recover (return to stable two-foot support)

1. Place the right foot back down (choose a clear contact: heel first, flat, or toe first).

2. Once contact is made, lock the right foot for a few frames (no drift).

3. Bring hips/root back toward center between both feet.

4. Reduce the hip tilt so the load redistributes.

Stability check: in front view, hips return to the middle; in side view, the character shouldn’t look like they’re pitching forward/back as the foot lands.

Checklist: stability in both views

Troubleshooting quick fixes

• Looks like hovering: lower hips slightly on the support side and ensure CoG projection is inside BoS.
• Foot slides during shift: re-key the planted foot to match its contact frame transform; move hips/root instead.
• One-foot pose feels impossible: widen stance in Pose 1–2 or shift hips further before lifting.
• Character tips forward when lifting: pull hips slightly back in side view or add a small torso counter-tilt.