PlayerController.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerController : MonoBehaviour {

    public float speed = 10;
    public float frequency = 1;
    public FootTarget leftFoot;
    public FootTarget rightFoot;
    public float speedInfluence;
    public float scaleLegHigh = 1;
    public float lengthStep = 2;
    public float ratioAnim = 0.3f;

    float distance = 0;

    // Use this for initialization
    void Start () {
		
	}
	
	// Update is called once per frame
	void Update () {
        var axes = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
        Vector3 delta = axes * speed;
        transform.position += delta * Time.deltaTime;
        var power = Vector3.Dot(transform.forward, axes.normalized);
        transform.forward = axes;
        var influencedTravel = delta.magnitude * Mathf.Clamp01(1 - delta.magnitude / speed * speedInfluence) * power;
        distance += Time.deltaTime * influencedTravel;
        if (delta.magnitude>0.5f) {
            UpdateFoot(distance, 1+influencedTravel, leftFoot);
            UpdateFoot(distance + frequency * 0.5f, influencedTravel, rightFoot);

        } else {
            SetFoot(leftFoot.item, GetFootPosition(leftFoot.offset), GetFootPosition(leftFoot.origin));
            leftFoot.previousPoint = GetFootPosition(leftFoot.offset);
            leftFoot.endPoint = GetFootPosition(leftFoot.offset);
            SetFoot(rightFoot.item, GetFootPosition(rightFoot.offset), GetFootPosition(rightFoot.origin));
            rightFoot.previousPoint = GetFootPosition(rightFoot.offset);
            rightFoot.endPoint = GetFootPosition(rightFoot.offset);
        }
    }

    void UpdateFoot(float distance, float forward, FootTarget target) {
        var alpha = distance / frequency;
        var currentCount = Mathf.Floor(alpha);
        if (currentCount!= target.count) {
            target.previousPoint = target.endPoint;
            target.endPoint = GetFootPosition(target.offset + Vector3.forward * forward * lengthStep*(1+ratioAnim));
        }
        var t = Mathf.Clamp01(Mathf.InverseLerp(0, ratioAnim, alpha%1));
        SetFoot(target.item, Vector3.Lerp(target.previousPoint, target.endPoint, t) + Vector3.up * Mathf.Sin(t*Mathf.PI) * scaleLegHigh, GetFootPosition(target.origin));
        target.count = currentCount;
    }

    void SetFoot(Transform item, Vector3 end, Vector3 start) {
        
        var dir = (start - end).normalized;
        var scale = (start - end).magnitude;
        var midpoint = (start + end) * 0.5f;
        item.position = midpoint;
        item.localRotation = Quaternion.LookRotation(dir, Vector3.up);
        item.localScale = new Vector3(0.3f, 0.3f, scale);
    }

    Vector3 GetFootPosition(Vector3 offset) {
        return transform.position + transform.TransformVector(offset);
    }

    [System.Serializable]
    public class FootTarget {
        public Vector3 offset;
        public Vector3 origin;
        public float count;
        public Transform item;
        public Vector3 endPoint;
        public Vector3 previousPoint;
    }
}