How to animate a wind generator rotor in code (varying rotation speed in runtime)

[dingaling007]

First post, go easy on me guys

Im trying to animate the rotor of a wind generator in code. But im trying to randomize the speed of the rotation to simulate a wind generator reacting to varying wind speeds. So one moment the blades might barely be spinning, next moment they might be spinning at high speed. and everywhere inbetween.

I’ve searched as best i can but i have not found an answer.

I have tried invoke repeating and random ranges but i cannot seem to get this working as desired.

using UnityEngine;
using System.Collections;

public class windGen1Rotate : MonoBehaviour {

void Start () {
InvokeRepeating (“rotateRotor”, 3, 2);
}

// Update is called once per frame
void Update () {

}

void rotateRotor()
{
float z = Random.Range (0f, 200f);
transform.Rotate (0, 0, z * Time.deltaTime);
}
}

[tonemcbride]

The problem with using a random range between 0 and 200 is that it’ll very quickly average to a value of 100 so the rotor will appear to move at a constant speed.

You’re better of using something like perlin noise which will give you much nicer random curves rather than the white noise you’d get from the random.range function. (Unity - Scripting API: Mathf.PerlinNoise)

[Hikiko66]

I would generate Bezier curves, and lerp through those
The Bezier curve points would obey contraints, that can be changed at runtime to make the wind more volatile/calm, or keep it within certain ranges.

You can use random range for the points (using the contraints)
You could use invoke to generate the beziers every x seconds and then take x seconds to lerp through a Bezier, but it’s even better if the speed of lerping through a bezier curve is also variable, because that gives you a much greater control over volatility.
In that case you wouldn’t use invoke.

Also, I would apply this to a windzone (controlling windzones requires reflection, but the scripts can be found on this forum), not to the rotor. I would then fetch the data from the windzone and apply it to the rotor indirectly.

That way the wind can be applied to particles/trees.

[jschieck]

Quoted from your duplicate post.

@""

There are several problems with your existing code. InvokeRepeating is only executing every 2 seconds, so the blades only rotate when that method is called, not every frame. You could the Update function and the Rotate function to accomplish the desired effect.

Another issue is that you are rotating on the Z axis exclusively, but not relative to the transform. So if you were to rotate your wind generator it would animate improperly. See the code below for a more robust, and customizable example.

using UnityEngine;
using System.Collections;

public class WindGeneratorRotator : MonoBehaviour
{
    // axis to rotate on
    public Vector3 axis = new Vector3(0, 0, 1);
    // the minimum and maximum speed the blade can rotate
    public Vector2 minMaxSpeed = new Vector2(100, 300);
    // how often the wind speed changes
    public Vector2 changeFrequency = new Vector2(10, 20);
    // how quickly the blade matches the new wind speed
    public float windChangeSpeed = 3;

    private float targetSpeed;
    private float currentSpeed;

    private void OnEnable()
    {
        currentSpeed = 0;
        StartCoroutine(Animate());
    }
    private void OnDisable()
    {
        StopAllCoroutines();
    }
    IEnumerator Animate()
    {
        while (enabled)
        {         
            // set an initial targetSpeed
            targetSpeed = Random.Range(minMaxSpeed.x, minMaxSpeed.y);
            // determine when to change the wind speed next
            float timeout = Time.time + Random.Range(changeFrequency.x, changeFrequency.y);         
            while (Time.time < timeout)
            {
                // interpolate the currentSpeed to match the targetSpeed
                currentSpeed = Mathf.Lerp(currentSpeed, targetSpeed, Time.deltaTime * windChangeSpeed);
                // rotate the blade every frame
                transform.Rotate(axis, currentSpeed * Time.deltaTime, Space.Self);
                yield return null;
            }
        }
    }
}

[Scabbage]

Perlin and Bezier are definitely nice ways of doing it, I was thinking more like setting a velocity at an interval and lerping between them:

public class WindGenRotator
{
    public bool enabled = true;
 
    float targetVelocity = 1f;
    float velocity = 1f;
    float rotation = 0f;

    public float maxVelocity = 4f;
    public float minVelocity = 0.1f;

    public float maxVelUpdateInterval = 3f;
    public float minVelUpdateInterval = 1f;

    void Start()
    {
        StartCoroutine(VelocityUpdate);
    }

    void Update()
    {
        velocity += (targetVelocity - velocity) * Time.deltaTime;
        transform.Rotate(transform.forward, velocity * Time.deltaTime);
    }

    IEnumerator VelocityUpdate()
    {
        while(enabled)
        {
            targetVelocity = Random.Range(minVelocity, maxVelocity);
            yield return new WaitForSeconds(Random.Range(minVelUpdateInterval, maxVelUpdateInterval));
        }
    }
}

Haven’t tested it, wrote it all in the post editor, but I think the general gist of it is pretty clear. The min/max update interval fields are for how frequently the velocity is changed.

EDIT: Dammit, @jschieck beat me to it ;p

[dingaling007]

Thanks Scabbage. Your code works nicely as does jschieck’s. I’m learning a lot here! Impressed you wrote that code without the editor, it was spot on except for a couple of parentheses on the coroutine call Lol. Seriously that’s awesome tho

Thanks tonemcbride, yep my code just had the rotor jumping to various states of rotation. Thanks for the idea regarding Perlin noise for the randomness it’s all good learning as an artist going into scripting.

Na ra Ku(updated:
Hikiko66)
. I really like this idea. I found having multiples wind generators running the above code the randomness ruined the illusion of having wind blowing thru when one wind generator spins fast and the other slow. Your idea sounds like it would fix this. I’m such a noob, but I’ll give it some serious effort.