How to animate material alpha property via script?

Question

I am creating Animator OverrideController via script based on current controller assigned to animator component. I have created animation curve for position and it works. When i try to animate transparency (material color alpha) it does not work (it does not make any effect, however in Animation Dopesheet there is yellow line: "Object name : Material.Color.a (Missing!)"). Did I fail to properly access this property or is it the consequence that creating animation via script works only for legacy animations with Animation component?

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class AnimationScript : MonoBehaviour {

    void Start()
    {
        AnimationClip clip = new AnimationClip();

        AnimationCurve curve = AnimationCurve.EaseInOut(0.0f, transform.position.x, 1.0f, transform.position.x);
        clip.SetCurve("", typeof(Transform), "localPosition.x", curve);

        curve = AnimationCurve.Linear(0.0f, 1.0f, 1.0f, 0.0f);
        clip.SetCurve("", typeof(Material), "_Color.a", curve);

        Animator anim = GetComponent<Animator>();
        AnimatorOverrideController animatorOverrideController = new AnimatorOverrideController(anim.runtimeAnimatorController);
        // "loop" is the name of clip not name of state
        animatorOverrideController["loop"] = clip;
        anim.runtimeAnimatorController = animatorOverrideController;
    }

}

However analogous code for legacy Animation component works:

void Start()
{
    Animation anim = GetComponent<Animation>();
    AnimationCurve curve;

    // create a new AnimationClip
    AnimationClip clip = new AnimationClip();
    clip.legacy = true;

    // update the clip to a change color
    curve = AnimationCurve.Linear(0.0f, 1.0f, 2.0f, 0.0f);
    clip.SetCurve("", typeof(Material), "_Color.a", curve);

    // now animate the GameObject
    anim.AddClip(clip, clip.name);
    anim.Play(clip.name);
}

What am I missing and why is first script not working?

Answer 1

Take a look at this. I'm not sure 100% but if you create a 'Color' in code, that is taken the same as your original color, then set the curve value to that color each frame, and finally set this as the color for "_Color". So perhaps change from using SetCurve to SetColor.

(Note: This doesn't answer your question exactly, but i still think it demonstrates a way to fix the problem):

ALSO: I expect you already have it set, but ensure the Material's Rendering Mode (in Inspector) is set to "Transparent" (it defaults as Opaque I think)

 Color transparentColor;

void Start(){
    Material mat = GetComponent<Renderer>().material;
    Color transparentColor = mat.color;
}

void Update(){
   // ... your code to set correct value to 'curve' here
   transparentColor.a = curve;

   mat.SetColor("_Color", transparentColor);

}