How to expand and fade game objects in Unity?

Questions & Answers
1

I want to expand fade 3d object after something collides it. I am beginner to unity and game development. As per my understanding we can do it in 3 ways:

  1. Using Animation window
  2. Using Particle System
  3. Using scripts in update method (by increasing size and making it invisible gradually)

Please suggest the optimized method to do this.

2

Hi raabaa,

I think the solution depends on what you are trying to do. Do I understand it correctly that you want your object after collision to 1) stop interacting 2) fade out over a time and 3) expand over time?

If this is the case, animating is certainly a possibility (but I am a programmer, so I prefer code :stuck_out_tongue: ), but I don’t know how to do it with a particle system.

Doing it with animation you just add an Animation (which is not the same as an Animator) component, create a new AnimationClip, add the properties Transform.scale, and Renderer.material.color (your material will need to be Fade type!), then at the final key position set the size (for all 3 components separately!) and the final color value. Then you have to play this animation from code in your collision detection, usually it is as easy as animator.Play() or animator.Play("<name of your animation>");

With code it is a bit simpler (for me): you declare variables for your transition duration and final size, then start a Coroutine that uses lerp:

[SerializeField] private float fadeOutDuration = 1f; // fades out in 1 second
[SerializeField] private float fadeOutSizeMultiplier = 2f; // doubles the size by the end

// call this when you want to expand-fade
private HandleCollision() {
    ownCollider.enabled = false; // disable your Collider to disable interaction with world; I assume you get it in Awake()
    ownRigidbody.isKinematic = true; // "disable" Rigidbody as well; again, get it in Awake()
    StartCoroutine(FadeOutExpand());
}

private IEnumerator FadeOutExpand() {
    // store original color and scale to be able to correctly scale
    Color originalColor = ownRenderer.material.color; // I assume you get ownRenderer in Awake()
    Vector3 originalScale = transform.scale;

    float t = 0;
    while (t < fadeOutDuration) {
        SetAlphaAndScale(originalColor, originalScale, t / fadeOutDuration); // passes value between 0 and 1
        yield return null;
        t += Time.deltaTime;
    }
    SetAlphaAndScale(1); // make sure you get the correct final size and color even with imprecise floating point and time
}

private void SetAlphaAndScale (Color originalColor, Vector3 originalScale, float t) {
    ownRenderer.material.color = new Color(originalColor.r, originalColor.g, originalColor.b, Mathf.Lerp(1, 0, t)); // assign a new color with decreasing alpha
    transform.scale = orignalScale * Mathf.Lerp(1, fadeOutSizeMultiplier, t); // scale relative to original size
}

Additionally, you might want to look into different interpolations, like Sinerp() and Hermite() which create smoother transitions at the end - see the extremely useful Mathfx from Unity Wiki!

(Btw, I feel honored for being personally called to help :slight_smile: )