Game Dev Combat Animation

The combat animation standard

The project copy is docs/combat-animation-standard.md (Thornvigil). Every rule is either measured by a test (test) or scored by the blind reviewers from rendered frames. When you add a move type (a spell cast, a staff slam, a monster bite), add its own numbered section and extend the tests. Never loosen a limit just to pass: change a limit only when a measured trade-off forces it, and write the reason beside it (see the elbow band in rule 12).

Every attack

1. Three phases on the game's clock.

   • The phases are anticipation (a readable wind-up that loads the body), the strike or release on the rule's contact frame, and a recovery back to the carried stance or a guard.

   • The strike is the fastest part. test: a sword tip peaks within 0.08 s of contact, and a bow's draw hand leaves the string faster than it ever drew.

2. The body drives the arms.

   • Hips before shoulders, shoulders before elbow, elbow before wrist, with the pelvis turning at least 15° across a melee strike. test.

   • A bow's loose is the exception: the recoil answers the release and never leads it.

3. Grounded feet. A step is a lift and a set-down, never a slide; the soles stay on the ground. test.

4. No dead holds over 0.25 s. A held pose breathes, trembles or settles.

   • The critics always flag frozen post-impact holds, even when the arm is fine.

5. Anatomy and silhouette.

   • No joint leaves its range or turns more than 35° in a frame. test (player-arm-anatomy).

   • The weapon reads against the body from every camera.

Arms and hands (rules 15–22)

Enforced on every frame of every strike, on both bodies, by tests/arm-ranges.test.js, sampled as gameplay samples them (30 Hz, gamePlayerMotion).

15. Elbows bend, never lock or fold shut.

    • The elbow stays between 10° and 152°.

    • Through the middle 80% of a strike, the sword or drawing arm keeps at least 20°.

    • At contact the sword hand is at least 60% of the arm's length from the shoulder: reach into the blow, but never lock.

16. Wrists stay in line.

    • The wrist bends at most 50° (twist removed) and rolls at most 45°.

    • A sword wrist is capped at 40° in the baker (WRIST_BEND 0.7 rad), and a drawing hand is held straight.

    • The forearm and shoulder carry the blade's line; the wrist only sets the edge.

17. No wringing. Forearm roll and upper-arm roll each stay at or under 52°.

18. No arm past 105° from hanging.

    • Measure it against the chest frame.

    • Shoulder skin crushes beyond it, so there are no overhead raises; a power shot sets just above the line.

19. The skin stays whole.

    • The worst 1% of each region's skin edges (upper arm, forearm, hand, fingers, each side) stretch at most 2× and crush at most 3× against the bind.

    • It is measured on the real skinned body mesh, every other frame.

    • This is the arbiter when a joint rule and a look disagree.

20. Hands are always in a pose.

    • A weapon hand closes on its grip.

    • A drawing hand hooks three fingers round the string with the thumb tucked, from the set to the loose and through the fly-back, relaxing only as it comes down.

    • An empty hand hangs relaxed. Never splayed, never clawed. test (hook beyond the relaxed hand).

21. Hands ride their shoulders.

    • A key's hand target is authored against the stance and travels with its shoulder as the trunk lunges and turns.

    • Between keys the hand swings in an arc about the shoulder.

22. Blade keys are reachable.

    • With a straight wrist a sword leaves the fist about 70° off the forearm, so a key's blade must lie 25–115° off its forearm.

    • Blade keys are world directions.

Melee (knight, sword and buckler)

6. The blade never passes through the head, the buckler or the ground.

   • It stays more than 8 cm clear of the skull.

   • The tip stays more than 18 cm above the ground (knight-measure.mjs reports the clearances).

7. The sword stays in front of the buckler.

   • The fist is never hidden behind the board and the blade never pierces it.

   • The board faces the foe in the cuts.

8. Quick strike (0.3 s to contact, 0.92 s total). In order:

   • a short chamber, laid back over the sword shoulder on a bent, raised elbow, with the hips turned back;

   • a diagonal cut down across the body, led by the hips as the forearm turns over;

   • a follow-through that keeps moving, the hand carried on to the shield-side hip on a bent elbow with the blade still on the line;

   • a return to a middle guard.

9. Heavy strike (0.67 s to contact, 1.57 s total). In order:

   • a rise onto the back leg, the blade laid back tip-up behind the sword shoulder on a bent elbow;

   • a step, and the hips dropping into the cut;

   • the blade coming over on the sword side of the head and crashing down on the line;

   • a sink across to the shield side and a rebound that folds the elbow;

   • a slow rise to guard.

• Hand speed stays at or under about 18 m/s between samples; anything faster is a pop, not a swing. test (continuous hand path). The rig's joints never snap more than 0.55 rad per sample.

• The blade at contact points through the target: forward more than 0.55, across more than 0.3, down more than 0.25. test.

Bow (archer)

The archery shot cycle as coached is stance, nock, set, set-up, draw, anchor, aim, release and follow-through.

10. The draw hand stays on the string.

    • From the set to the release, the fingers stay within 6 cm of the line from the grip to the anchor.

    • The string is drawn back at least 35 cm.

    • The drawn string follows the fingers on both surfaces, and the bow rolls about its stave so the string faces the anchor.

11. A nocked arrow is visible from the set to the release, never at rest and never after the loose.

12. Anchor under the jaw, beside the chin (src/bow-anchor.js).

    • At full draw the fingers are within 8 cm of the anchor and never behind the head.

    • The draw elbow sits behind the hand, within 8 cm under the arrow. The band was widened from 5 cm because a higher elbow crushes the draw shoulder's skin past rule 19 on this rig.

    • The bow arm stays long (elbow bend under 25°).

    • test: the face's forward and down come from the standing body, not the bone's axes, and the fingers stay in front of the head through the draw.

13. Side-on stance, head on the line.

    • The hips and chest turn toward side-on during the set (hips about −0.62 rad at full draw).

    • Once the shot is away, the stave passes at least 15 cm to the side of the face.

14. The release snaps.

    • The string springs home at once.

    • The draw hand flies back along the jaw and out past the shoulder, elbow bent behind, never up round the back of the head.

    • The bow arm holds on the line for a beat, then lowers.

    • The hand comes down beside the body along a continuous path, never flung or wrapped behind the back.

    • The power shot holds a longer, trembling full draw and recoils harder.

    • test: the loose outpaces the draw, and the hand flies at least 5 cm past the jaw.

Adapting to a new move type

• A staff, spell or two-handed weapon. Write its phases and contact on its rule clock. Add its prop clearance (head, ground, off-hand) to a measure probe, and add the move to MOVES in arm-ranges.test.js. Every arm rule applies unchanged.

• Monsters. These have their own rigs. Re-derive the arm lengths, the shoulders, and every bone-local axis from mesh landmarks before reusing any number here.