Rotation around an axis, how unity handle this?

Questions & Answers
1

Im trying to rotate a transform on his axis via C#. But when executed this really not move… Can someone explain me why? How quaternions works?
Im using this code (later ill add a non frame rate dependent mode.)

public GameObject SunComponent;

void Start()
    {
        LightComponenet = SunComponent.GetComponent<Light>();
    }

void Update()
    {
        SunRotation = SunComponent.transform.rotation.x;
        SunRotation = SunRotation++;
    }

I was expecting the objec rotating really fast, instead it simply not moves… Why?

2

Because “SunRotation” is NOT the object’s transform. After you increase SunRotation, you need to apply it to the gameObject:

 SunComponent.transform.rotation.x = SunRotation;
3

I’m assuming SunRotation is defined as an int somewhere.

SunRotation = SunComponent.trasnform.rotation.x

The above assigns the value of x to SunRotation as it is not a reference, but a value type. Any changes to SunRotation won’t be applied back to the value in SunComponent as it has copied the value to your new variable SunRotation.

To re-apply the value you need to manually set the value in SunComponent:

SunComponent.transform.rotation.x = SunRotation;

or even faster just :

SunComponent.transform.rotation.x++;

As a quick note on formatting, variables should be camelCase and methods/classes should be CamelCase

This Code will just make the sun rotate about itself however. If you’re trying to get it to rotate about a point its slightly more complicated. To get the sun to move in an arc over the centre of the terrain i implemented the following and attached the script to my sun object:
public class SunMove : MonoBehaviour
{

    GameObject terrain;
    public float speed;
    float terrainLength;
    float terrainWidth;
    float angle;
    float radius;
    float cos;
    float sin;
    Vector3 centre;
    float sinRad;
    float cosRad;
    // Use this for initialization
    void Start()
    {
        terrain = GameObject.FindGameObjectWithTag("Terrain");
        if (speed == null)
        {
            speed = 0.01f;
        }
        terrainLength = terrain.GetComponent<Terrain>().terrainData.size.z;
        terrainWidth = terrain.GetComponent<Terrain>().terrainData.size.x;
        transform.position = new Vector3(terrainWidth * 0.5f, 0, 0);
        angle = 0f;
        centre = new Vector3(terrainWidth * 0.5f, 0, terrainLength * 0.5f);
        radius = Vector3.Distance(centre, transform.position);
    }

    // Update is called once per frame
    void Update()
    {
        if (speed != 0)
        {
            angle += speed;
            cos = Mathf.Cos(angle);
            sin = Mathf.Sin(angle);
            sinRad = sin * radius;
            cosRad = cos * radius;
            gameObject.transform.position = new Vector3(centre.x, sinRad + centre.y, cosRad + centre.z);
            
        }
        else
        {
            transform.position = new Vector3(centre.x, 125, -125);
        }
        gameObject.transform.LookAt(centre);
    }
}
4

Solved this problem by myself (after two hours of study about quaternoins and euler angles.)

The solution is really simple: converting quaternions to vector3 angles (eulers) and applying the result. In code is really simple:

public class SunTime : MonoBehaviour {
    public Vector3 SunRotation = new Vector3 (1, 0, 0);
    public GameObject SunComponent;

    //Each update i add 1 euler rotation on the X axis.
    void Update()
    {
        SunComponent.transform.Rotate(SunRotation);
    }
}