Grasshopper

import { createAsset } from 'https://gaitkit.com/cdn/grasshopper.mjs';
import { walker } from 'https://gaitkit.com/runtime/walk.mjs';

const grasshopper = createAsset();
scene.add(grasshopper);                      // rests on y = 0, front faces +Z
const gait = walker(grasshopper, { ground: (x, z) => terrainHeight(x, z) });   // or omit ground for a flat floor

let dist = 0;
renderer.setAnimationLoop(() => {
  dist += speed * clock.getDelta();
  grasshopper.position.z = dist;
  gait.poseAt(dist);                  // feet stay planted, at any frame rate
  renderer.render(scene, camera);
});

import { useMemo, useRef } from 'react';
import { useFrame } from '@react-three/fiber';
import { createAsset } from 'https://gaitkit.com/cdn/grasshopper.mjs';
import { walker } from 'https://gaitkit.com/runtime/walk.mjs';

export function Grasshopper({ speed = 1 }) {
  const model = useMemo(() => createAsset(), []);
  const gait = useMemo(() => walker(model), [model]);
  const dist = useRef(0);
  useFrame((_, dt) => {
    dist.current += speed * dt;
    model.position.z = dist.current;
    gait.poseAt(dist.current);                  // feet stay planted, at any frame rate
  });
  return <primitive object={model} />;
}

# Import grasshopper.glb (download below). It carries an in-place "Walk" animation.
@onready var anim: AnimationPlayer = $Grasshopper/AnimationPlayer

func _physics_process(delta):
    velocity = transform.basis.z * speed
    move_and_slide()
    anim.play("Walk")
    anim.speed_scale = speed / 0.019   # Walk clip covers 0.019 m/s at 1x

// Import grasshopper.glb with glTFast (com.unity.cloud.gltfast).
animator.Play("Walk");
animator.speed = speed / 0.019   // Walk clip covers 0.019 m/s at 1x