How to expand and fade game objects in Unity?

Question

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:

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

Please suggest the optimized method to do this.

Answer 1

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 :P ), 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 :) )

How to expand and fade game objects in Unity?

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