How to moved a fixed amount per key press using first person character controller

Question

I'm trying to write a simple 1st person character controller that stays on a grid (ie. turning 90 degrees per side keystroke, and moving 2 metres per forward/back keystroke. I've come up with the code below, in an attempt to cap each move to 2m. When i use Time.deltaTime, the distance moved fluctuates inconsistently around 2m. When i use Time.fixedDeltaTime, the distance moved is consistent, but is over 2 metres.

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent (typeof(CharacterController))]
 
 public class FPCSteps : MonoBehaviour {
 
     float temp;
     bool isRotating;
     int horizontalDirection;
 
     float temp2;
     bool isMoving;
     int forwardDirection;
 
     CharacterController characterController;
 
     
     // Use this for initialization
     void Start () {
         Screen.lockCursor = true;
         characterController = GetComponent<CharacterController> ();
             
     }
     
     // Update is called once per frame
     void Update () {
 
         if (Input.GetKeyDown (KeyCode.W) && !isMoving) {
             isMoving = true;
             forwardDirection = 1;
             temp2 = 0;
         }
 
         if (Input.GetKeyDown (KeyCode.S) && !isMoving) {
             isMoving = true;
             forwardDirection = -1;
             temp2 = 0;
             
         }
 
         if (Input.GetKeyDown (KeyCode.D) && !isRotating) {
             isRotating = true;
             horizontalDirection = 1;
             temp = 0;
         }
         if (Input.GetKeyDown (KeyCode.A) && !isRotating) {
             isRotating = true;
             horizontalDirection = -1;
             temp = 0;
         }
 
         transform.Rotate (Vector3.up * 90 * Time.fixedDeltaTime * horizontalDirection, Space.World);
         temp += 90 * Time.fixedDeltaTime;
         if (temp >= 90) {
             temp = 0;
             horizontalDirection = 0;
             isRotating = false;
         }
 
         Camera cam = Camera.main;
         characterController.Move (cam.transform.forward * forwardDirection * 2 * Time.deltaTime);
         temp2 += 2 * Time.deltaTime;
         if (temp2 >= 2){
             temp2 = 0;
             forwardDirection = 0;
             isMoving = false;
         }
 
     }
     
 }

Sorry if there's something obvious i've missed, i'm still very new and clueless about C#. If anyone can help, or point me towards a resource that might help, it would be greatly appreciated!

Answer 1

There is no issue here related to C#, but there is an issue here to your approach. Your grid movement is trying to place your character at a precise place, but your code is using relative movements. First it is using the relative direction of 'cam.transform.forward'. Second, each move is relative to the last. And finally you are using Time.deltaTime where the time from frame to frame will change. With floating point imprecision added in, even if you could working out the current issues with your code, over time a error will creep in. If it were me, I'd make the following changes.

While not strictly necessary, I'd change the grid to 1 x 1 rather than 2 x 2. This might mean changing the distance or the FOV of the camera and/or resizing elements, but it just makes debugging and rounding easier.
When moving calculate an absolute position. Note I'm confused about the use of 'cam.transform.forward'. Using this value only makes sense if the camera will be rotating. Use absolute directions or values instead. For example, if you press the 'A' key, you will subtract 1.0 from the 'x' value of the current position to generate the new goal position. Or alternately you can add Vector3.left to your current position to get the goal.
Round the new goal position: 'goalPos.x = Mathf.Round(goalPos.x);' This will eliminate errors creeping in over time.
For each move, first calculate the move. Then test the distance against the remaining distance. If the remain distance is shorter, use that instead:

Vector3 dir = goalPos - transform.position; Vector3 move = dir.normalized Time.deltaTime speed; if (move.magnitude > dir.magnitude) { characterController.Move (dir); isMoving = false; } else { characterController.Move(move); }

'speed' will be a variable you define and will represent units of movement per second.

How to moved a fixed amount per key press using first person character controller

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