Chapter 4: Center of Gravity & Stance for Believability

Created by Sarah Choi (prompt writer using ChatGPT)

Center of Gravity & Stance for Believability

Body Plans & Silhouette Families for Creature Concept Artists

A creature can have beautiful details and a stunning silhouette, but if it looks like it’s about to tip over, players will feel something is “off” before they can articulate why.

That “off” feeling usually comes from problems with center of gravity (CoG) and stance.

As a creature concept artist, understanding CoG is not about doing physics homework—it’s about learning to place weight convincingly. A believable stance:

  • Grounds the creature in its world.
  • Communicates personality and combat role.
  • Helps animators, riggers and designers trust your design instead of fighting it.

In this article we’ll explore CoG and stance across four major body‑plan families:

  • Vertebrate
  • Arthropod
  • Cephalopod
  • Hybrid

We’ll keep both the concepting side (gesture, silhouette, character) and the production side (rigging, animation, physics, collision) in view, and we’ll stay grounded in practical tools you can apply directly to your thumbnails and callouts.

1. The Concept Artist’s Version of Center of Gravity

You don’t need to calculate equations to use CoG effectively. For our purposes, center of gravity is:

The point where the creature’s mass feels concentrated and where gravity “pulls” it straight down.

The core visual rule:

For a stable stance, the CoG should project down into the area framed by its supporting limbs (its base of support).

If the CoG sits outside that base, the creature looks like it’s about to stumble—unless it’s clearly in motion.

1.1 The Base of Support

The base of support is the area on the ground between and under the contact points of the supporting limbs:

  • A biped: roughly a rectangle between both feet.
  • A quadruped: a four‑point polygon between all four feet.
  • Many‑legged arthropod: often a continuous “rug” under the body.

When you sketch a stance, you can quickly:

  1. Mark where the feet, claws, hooves or tentacle tips touch the ground.
  2. Connect those points in your mind (or lightly on a separate layer).
  3. Drop an imaginary line straight down from the creature’s mass center (usually somewhere around the chest/hips region).

If that line falls outside the polygon for a “rest” pose, the creature feels unstable.

1.2 Static vs Dynamic Balance

Not all poses should look perfectly stable.

  • Static balance: Idle, resting, guarding. CoG sits comfortably inside the base of support.
  • Dynamic balance: Running, lunging, leaping, taking off. CoG may move toward or beyond the front edge of the base, suggesting momentum.

For concept art:

  • Use static balance for orthos, design sheets, and production callouts.
  • Use more dynamic CoG placement for key art, action poses, and cinematic frames.

Production artists rely on your neutral, static pose to understand how the creature stands when doing nothing special. That neutral stance must look physically possible.

2. Visual Tools for CoG and Stance

Here are simple visual shortcuts you can use in every sketch.

2.1 The “Bowling Pin Test”

Imagine your creature is a bowling pin:

  • If you nudge it a little, does it feel like it would rock back to center or topple?

To check:

  • Draw a small vertical line down from the chest/hip mass.
  • See if it falls between the main support limbs.

If that line lands ahead of the front foot or behind the back foot in a neutral pose, the creature feels like it would fall.

2.2 Weight Path: From Spine to Ground

Think of the weight path as the route gravity takes through the body:

  • Spine → hips/shoulders → legs → ground.

A believable stance has a continuous chain of support:

  • Bent knees and hocks under the hips.
  • Shoulders roughly over forelimbs for quadrupeds.
  • For bipeds, hips over feet; knees not hyper‑locked backward.

If joints zigzag in impossible ways (e.g., knees bending wrong, legs angling away from CoG), the eye senses instability even if the silhouette is cool.

2.3 Contact Poses and Foot Angles

Feet tell you where weight is really going.

  • Flat, planted feet → weight bearing and stable.
  • On toe tips or claws → light contact, readiness to move.
  • Tilted feet or half‑lifted toes → transition, motion, or slipping.

In static orthos and design callouts:

  • At least two main support limbs should look clearly planted.
  • Toes or claws should align roughly opposite the direction of the CoG lean.

3. Vertebrate CoG & Stance

Vertebrates are the easiest place to learn CoG logic because we intuitively understand how they stand.

3.1 Vertebrate Body Plans & Weight Distribution

Vertebrates usually break into:

  • Head & neck
  • Torso / ribcage
  • Pelvis / hips
  • Tail (optional)

CoG often sits:

  • Under the ribcage for quadrupeds.
  • Between hips and chest for bipeds.

The tail acts as a counterbalance:

  • Heavy tails can move CoG backward.
  • Long necks and big heads push CoG forward.

As a concept artist, you decide how these parts push and pull the CoG.

3.2 Quadruped Stance Patterns

Common quadruped stances:

  1. Neutral/standing
    • Forelimbs roughly vertical under shoulder mass.
    • Hind limbs under hips, often slightly tucked.
    • CoG projection lands in the middle of the polygon formed by four feet.
  2. Predatory/ready
    • Body pitched slightly forward.
    • Forelimbs angled, hind limbs crouched, tail used as dynamic balance.
    • CoG creeps toward the front of the base but stays inside.
  3. Heavy/tank
    • Wide foot placement.
    • Legs more vertical to support mass.
    • CoG sits low and centered, giving a grounded, immovable feel.

Silhouette considerations:

  • A forward‑leaning silhouette with CoG nearer the front feet feels aggressive, predatory.
  • A balanced or slightly back‑leaning silhouette feels cautious, defensive, or noble.

Production‑side:

  • Quadrupeds with a believable neutral stance are easier to animate for walking and idle cycles.
  • Extreme leg poses in the concept can be misread as the neutral position; clearly label hero action poses vs rest poses.

3.3 Bipedal Vertebrates

Bipeds (humanoids, theropods, raptor creatures) must keep CoG projected between the two feet.

Visual tips:

  • Draw a simple pelvis block and ensure it doesn’t extend way past the feet.
  • When the torso leans forward, the legs and feet must slide forward under it.
  • Bent knees and ankles help keep CoG balanced—straight up and down “stick legs” often look stiff or top‑heavy.

Dynamic gestures (leaning, lunging) are fine, but remember:

  • For neutral orthos, keep CoG clearly between the feet.

Production‑side:

  • Animators will base walk cycles on the neutral stance. If it’s pitched too far, cycles may look like the creature is always about to fall.

3.4 Tails, Horns & Extra Mass

Big horns, heavy weapons, armor packs, and massive tails all shift perceived CoG.

When adding them:

  • Visually “compensate” with stance: more widely spaced feet, more bend in the legs, tail used like a third support.
  • Make sure the direction of lean and ground contact supports the implied weight.

In production:

  • Extra mass means more to consider for physics, collision, and clipping. A good neutral stance gives technical artists a stable starting point.

4. Arthropod CoG & Stance

Arthropods (insects, arachnids, crustaceans, myriapods) have many legs and often an exoskeleton. That gives them a wide base of support—but it also tempts artists to place legs arbitrarily.

4.1 Many Legs, Many Supports

With 6, 8 or more legs, arthropods can maintain stability even while lifting several limbs.

For a neutral stance:

  • The body mass (cephalothorax + abdomen) should hover above a dense region of leg contact.
  • Legs can be splayed, but not so far that the body floats out past the center.

Visual strategy:

  • Sketch a simple oval body and drop a CoG mark near its center.
  • Place leg bases so that if you connect their feet, most of that oval is over the polygon.

4.2 Elevation & Clearance

Two main arthropod stance types:

  • Low scuttlers: body very close to the ground, legs bent outward and slightly downward (crabs, many spiders).
  • High stalkers: body elevated on long legs (mantises, some spiders).

For low stances:

  • CoG sits low; small shifts feel stable and heavy.
  • Great for tanky enemies and ambush predators.

For high stances:

  • CoG is high above a narrow base; they feel agile but less stable.
  • Emphasize careful leg placement in silhouette to maintain believability.

Production‑side:

  • High, thin legs demand careful rigging to avoid foot sliding and unnatural bending.
  • Wide, low stances can cause more ground clipping issues if not clearly defined.

4.3 Leg Rhythm & Weight Transfer

Because arthropods have many legs, players read rhythm as a cue for movement type:

  • Even, repeated leg spacing → relentless, mechanical motion.
  • Uneven leg spacing → more character, but potentially unstable if CoG is not considered.

When designing:

  • Think about which legs are primary weight bearers vs smaller support legs.
  • Give primary legs clearer anchoring under the body.

Production:

  • Animators may choose a gait pattern (alternating tripods, wave‑like leg lifts). Your cockpit art benefits from legs being placed logically for those patterns.

5. Cephalopod CoG & Stance

Cephalopods (squid, octopus, cuttlefish, nautilus) challenge our everyday intuition. They can float, jet, or crawl using tentacles.

5.1 Floating & Neutral Buoyancy

Many cephalopod‑inspired game creatures are designed as floaters:

  • Mantle or central body mass suspended in water, air, or magical field.

For these, CoG still matters, but:

  • It’s about rotational balance rather than falling over.

Visual cues:

  • If mantle is large, CoG likely sits near its center.
  • Tentacles or fins radiate around it, but the creature appears to “hang” from that mass.

To imply stable float:

  • Align the longest limbs downward, as if gently pulled by gravity.
  • Keep the central mass vertically above the average limb spread.

Production‑side:

  • Rigs may use simple floating motion cycles with some secondary tentacle simulation. A clear CoG helps animators decide how the body lags and leads.

5.2 Ground‑Crawling Cephalopods

When cephalopods move along surfaces, tentacles become legs.

Believable stance:

  • Tentacle bases cluster around the mantle.
  • Several tentacles contact the ground like a tripod or multi‑leg arthropod.

Visual strategy:

  • Imagine the mantle as the main mass; drop an imaginary CoG.
  • Place tentacle contact points so that CoG sits well within the footprint of these contacts.

Production‑side:

  • Crawling cephalopods are complex to rig; clear tentacle groupings used for ground contact help define animation responsibilities.

5.3 Hybrid “Float & Step” Designs

Some creatures float but also step or anchor tentacles.

To keep stance believable:

  • Decide whether the creature is mostly floating (tentacles lightly touching) or mostly stepping (tentacles bearing weight).
  • Design the stance to match: either CoG near the center of a roughly circular tentacle footprint, or suspended slightly above a contact zone.

6. Hybrid CoG & Stance

Hybrids mix vertebrate, arthropod, and cephalopod logic: a dragon with insect legs; a crab with a humanoid torso; a floating jellyfish with vertebrate limbs.

The danger is that you get excited by cool parts and forget whether the creature can stand.

6.1 Choose the Primary Locomotion System

Ask first:

Is this creature fundamentally standing like a vertebrate, an arthropod, or a cephalopod?

Whichever you choose:

  • Use that family’s stance rules for CoG and base of support.
  • Treat additional limbs as supports, displays, or weapons, but not the primary system.

Examples:

  • Vertebrate‑primary: A centaur‑like creature with extra arthropod limbs attached to the thorax; CoG still rests over four main legs.
  • Arthropod‑primary: A crab‑body with a human torso; CoG sits over broad crab legs, human upper body acts as a tower, not an extra support.
  • Cephalopod‑primary: Floating mantle with a pair of vertebrate legs dangling below; stance rules follow floating logic, legs mostly decorative.

6.2 Hybrid Stance Pitfalls

Common problems:

  • Legs attached in places where they couldn’t actually bear weight (e.g., tiny limbs sprouting from armor plates with no skeletal connection).
  • Multiple incompatible leg systems (e.g., digitigrade hind legs and crab legs both trying to be main supports).

Fixes:

  • Simplify: identify one leg set as main supports, make others visibly smaller or positioned where they clearly play secondary roles.
  • Adjust proportions: enlarge or thicken the primary limb group so they feel capable of holding the mass.

Production‑side:

  • A clear primary locomotion system makes rigging and animation design much more efficient.
  • Secondary limb sets can share simpler rigs, limited motion, or physics‑based motion.

7. Stance, Personality & Role

CoG and stance are not just physics—they’re acting.

You can use them to express:

  • Role: tank vs skirmisher vs caster vs support.
  • Personality: cocky, timid, disciplined, feral.

7.1 Role Reads

Tank / bruiser:

  • Low CoG.
  • Wide stance, feet spread farther apart.
  • Legs more vertical, bearing huge weight.
  • Tail (if any) close to the ground as an extra stabilizer.

Skirmisher / assassin:

  • CoG somewhat higher, ready to shift.
  • Limb angles more acute, joints bent for spring.
  • Narrower stance, suggesting agility over raw stability.

Caster / support:

  • Stances may be more upright, with CoG centered but not crouched.
  • Legs stable enough, but weight emphasis might be on torso/arms or floating structures.

7.2 Personality Reads

  • A confident creature stands with CoG comfortably supported, no excessive crouch.
  • A timid creature keeps CoG back, limbs closer to the body, ready to retreat.
  • A feral/aggressive creature leans CoG forward, as if ready to pounce.

For production:

  • These CoG choices tell animators how the idle cycles should feel: relaxed sway, tense coil, etc.

8. Silhouette, CoG & Stance Together

CoG is invisible, but silhouette shows its effects.

When you look at a creature in pure black:

  • You should be able to guess where it’s heavy.
  • You should sense whether it’s grounded, leaping, or off‑balance.

Silhouette tips:

  • Use larger masses low and central for grounded designs.
  • Use elongated masses (neck, tail, wings) with a stable core to suggest dynamic range without losing balance.
  • Ensure the footprint (the shape on the ground made by feet) feels adequate to support the visible mass.

Production‑side:

  • Good stance silhouettes lead to more readable animations and better player readability in game cameras.

9. Workflow: Designing Credible Stances

Here’s a practical, step‑by‑step workflow you can apply to any creature.

Step 1 – Rough Masses First

Before adding details:

  • Block in the head, torso/mantle/central body, hips/abdomen, and big appendages as simple shapes.
  • Mark an approximate CoG—usually somewhere inside the largest combined body mass.

Step 2 – Choose Stance Type

Decide:

  • Static idle vs dynamic action.
  • Tank vs skirmisher vs caster.
  • Primary body plan (vertebrate, arthropod, cephalopod, hybrid).

This guides how low or high the CoG should feel.

Step 3 – Place Support Limbs

Now add legs/tentacles/anchors:

  • Make sure at least two or three main supports surround the CoG when viewed from above.
  • Adjust foot placement until the CoG projection falls well within the base of support for a static pose.

Step 4 – Check from Multiple Angles

Even if you only show one final view, thumbnail roughs from:

  • Side view.
  • 3/4 front.
  • Top‑down (super simplified).

In each, check whether the CoG still looks supported.

Step 5 – Refine Silhouette & Ground Contact

Sharpen the pose:

  • Clarify which feet are fully planted.
  • Adjust limb angles to look tense, relaxed, or ready.
  • Clean up negative spaces between limbs, making sure they reinforce the stance rather than muddy it.

Step 6 – Annotate for Production

In your handoff or callouts, you can:

  • Indicate neutral stance vs action poses.
  • Mark where most weight rests (front‑heavy, rear‑heavy, evenly distributed).
  • Note if any limbs are non‑weight‑bearing (e.g., wings, decorative tentacles).

This tells animators how to prioritize rigs and what kind of movement you imagined.

10. Body‑Plan Specific Exercises

10.1 Vertebrate Exercise – Fix the Top‑Heavy Beast

Take a design of a bulky quadruped or biped that looks a bit cartoony or top‑heavy.

  • Draw a vertical CoG line from its chest/torso.
  • Adjust foot placement and leg bend so that line clearly falls between supports.
  • Compare before and after side‑by‑side silhouettes.

10.2 Arthropod Exercise – Stable vs Unstable Pose

Draw a six‑legged insectoid creature in two ways:

  • Very stable, tank‑like stance.
  • High, precarious stance.

Keep body proportions identical; only change leg angles and contact positions. Notice how much stance alone changes the role read.

10.3 Cephalopod Exercise – Float vs Crawl

Design a cephalopod creature in two modes:

  • Floating idle in water or air.
  • Crawling along a surface.

In each mode:

  • Mark CoG.
  • Place tentacle contacts accordingly.

Observe how limb grouping and posture shift even though the basic anatomy stays the same.

10.4 Hybrid Exercise – Choose a Primary Stance Logic

Design a hybrid creature (e.g., arthropod lower body, vertebrate upper body).

  • First draw it in a way that feels awkward or unclear.
  • Then redraw with a deliberate choice: “stands like a crab” or “stands like a horse,” etc.
  • Adjust limbs and CoG so one system clearly dominates.

Compare which version feels more believable.

11. Closing Thoughts

Center of gravity and stance aren’t just technical trivia—they’re part of the visual grammar that makes your creatures feel like they truly belong in their worlds.

As a concept‑side artist, CoG and stance help you:

  • Make designs that feel solid and intentional, not floaty or accidental.
  • Convey role and personality through posture alone.
  • Build coherent silhouette families across vertebrate, arthropod, cephalopod, and hybrid body plans.

As a production‑side concept artist, they help you:

  • Deliver designs that animators and riggers can trust and build on.
  • Avoid last‑minute redesigns when characters fail physical believability tests.
  • Communicate clearly about how your creatures stand, move, and shift weight.

Each time you sketch a new creature, try asking:

  • Where is its weight really sitting?
  • Which limbs are actually holding it up?
  • Does this stance match its role and personality?

If you can answer those questions confidently—and your silhouettes still look cool—you’re not just drawing creatures. You’re designing believable, game‑ready beings whose body plans and stance logic will hold up from thumbnail scribbles all the way to shipped animations.