Question Why do other unrelated parameters fluctuate minutely?

I'm completely new to Unity and C#.
I'm using Google Translate to ask the question, so please forgive me if my sentences may be weird.

Why do other parameters other than the z-axis move slightly while running the code below?
I can understand that there will be a slight difference in the z-axis, but I don't understand why the x- and y-axes are affected.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class PlayerControl : MonoBehaviour
6. {
7.     // Start is called before the first frame update
8.     void Start()
9.     {
10.        
11.     }
12.  
13.     // Update is called once per frame
14.     void Update()
15.     {
16.         //Move the vehicle forward
17.                 transform.Translate(Vector3.forward * Time.deltaTime * 20);
18.     }
19. }
20.  

 

I'll let others who know better answer the question. My best guess would be that this happens because of the Vector3 used in the code line and the fact that it uses floats not integers.
Welcome to Unity!
Edit: what is your mother tongue?

 

Is your vehicle object a child of something else? That would be my guess. Though the difference is just 0.00001 and 0.0000002, so almost 0. So without more background we can't really tell.

 

Google floating point precision, its normal.

 

Translate may be a matrix operation which means all axis are affected even the ones that don‘t change. And what you see fluctuating is precision issues due to floating point having a limited, not infinite, accuracy as others pointed out.

The same precision issue causes all kinds of weird snapping or offset issues for transforms, animations, a
shadefs, etc to varying degrees when an object is 5000+ units away from origin.

 

thank you everyone!
Vehicles are not child.
Unrelated axes also change slightly due to floating point and matrix operations!
I was convinced!

My native language is Japanese

 

素晴らしい！私は日本語を勉強しています。

(Translation: Great! I'm learning Japanese.)

 

Bingo. By default it is also

relativeTo = Space.Self

so that means it is multiplied by the matrix before being added to the position, same as if it was translated by

transform.forward

.

I really love that OP used a translator to report problems with transform.Translate()... more proof that we live in a simulator.

Your sentences are fine! Welcome!

 

I don't believe it's Translate or floating point precision. I did a little test and I got zero deviation on the x and y. The only thing I could do to recreate this was to place the script on a cube with a rigidbody. And even then I only get slight deviation on the y axis. It wasn't until I enabled gravity and let the cube slide along the "ground" that I started to see obvious deviation.

 

Rigidbodies tend to do that but the op didn't mention that. And his code suggests no rigidbody involved.

 

Rigidbody is enabled.
Does this affect the fluctuation?

 

When scripting a rigidbody you're supposed to use methods like AddForce().

 

From what I've noticed, yes. And, as already said, using transform.Rotate is inappropriate.
You either need to remove the rigidnidy or use the proper scripting. Here is the documentation: https://docs.unity3d.com/ScriptReference/Rigidbody.html

In Japanese: https://docs.unity3d.com/ja/current/ScriptReference/Rigidbody.html

 

I see!
After deleting the rigid body, values other than the Z axis no longer change.
Thank you very much! ! ! !