Changing a shader blend on pointer click over time

Question

I have a shader in Unity that is set up to blend between two textures. This is set up and works fine.

Blend has a range from 0-1 and works well on offline mode.

    _Blend1("Blend between _MainTex and Texture2", Range(0, 1)) = 0

I have set up an OnClick pointer that works fine. It essentially toggles a value to true and activates it in the Update. I have had some success on toggling the values between 0 (The first texture and 1 (The second texture).

    public void OnColorChangeClick()
{
    if (newSwitchOne)
    {
        switchOn = true;         
    }
    else if (newSwitchTwo)
    {
        switchOff = true; 
    }
}

In the update when switchOn is true I have a while loop that runs and increments a count for the blend.

 void Update()
{
    rend.material.SetFloat("_Blend1", up);
    while (switchOn == true) {
        for (int i = 0; i < 10; i++)
        {
           //StartCoroutine(Wait());
            up = Time.deltaTime * (up + 0.1f);
        }
        switchOn = false;
        print(switchOn);
    }
}

The trouble I am having is that the value increments are not working alongside time.deltaTime. I am seeing that Time.deltatime may not work in a while loop. So I have also tried a CoRoutine with a WaitForSeconds. None of this is giving me the incrementation that I desire.

I have looked into Lerping this - but I'm not aware how to Lerp such a value - I have been looking, perhaps in the wrong places.

Can someone point me in the right direction?

Can't believe no answer mentioned this in all these answers. The issue in your code is because your are using `Time.deltaTime` in the `Update` function which is a void function. `Time.deltaTime` will not change in the `Update` function. Move all those code into a coroutine(`IEnumerator`) function then add `yield return null` to the end of the `while` loop, your problem should be solved. — Programmer, Aug 25 '17 at 17:31
Thank you for your comment Programmer. Right I need to read up on time.deltatime a bit more. I've been taking this for granted. — Mark Quinn, Aug 25 '17 at 17:58
No problem. You also need to learn coroutine too since you need them when it comes to [doing something over time](https://stackoverflow.com/questions/45736799/decrease-variable-over-a-specific-amount-of-time/45737410#45737410) otherwise you do it in the Update function which will run forever instead of "run then end". Happy coding! — Programmer, Aug 25 '17 at 18:04
I am familar with corotuines with waitforseconds - problem was it just wasn't playing ball and I wasn't seeing the problem! There was a clash. I'll get there. But thank you all the same - the responses help :) — Mark Quinn, Aug 25 '17 at 18:07

Draco18s no longer trusts SE · Answer 1 · 2017-08-26T07:52:40.010

2

Update() already runs "over time." You don't need a for loop or a coroutine. You just need to track a variable that changes inside the Update() method body.

up = Time.deltaTime * (up + 0.1f);

Oh wait, you already do.

void Update()
{
    rend.material.SetFloat("_Blend1", up);
    if(switchOn == true) {
        up = Time.deltaTime * (up + 0.1f);
        if(up >= 1) {
            switchOn = false;
        }
        print(switchOn);
    }
}

Ta da.

However, you still need code to bring the value back down again (either animating it back to 0 or just setting it to 0) but your original code didn't have it either, so I'm not including it.

edited Aug 26 '17 at 07:52

answered Aug 25 '17 at 15:37

Draco18s no longer trusts SE

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Side note: You may want to look into [Material Property Blocks](https://docs.unity3d.com/ScriptReference/MaterialPropertyBlock.html) at some point. By directly modifying the shader value you're actually *cloning the material* which results in memory wastage and breaks batching. – Draco18s no longer trusts SE Aug 25 '17 at 15:39
Thank you for your feedback Draco - your help is appreciated. Sadly this code crashed my system. I thought I was being silly but tried it out a few times and it looks appropriate to me. Regardless thank you for this and the heads up on the Material Property Blocks. Many miles for me to go! – Mark Quinn Aug 25 '17 at 16:32
@MarkQuinn Remove the while loop. I didn't notice it (edited answer). – Draco18s no longer trusts SE Aug 26 '17 at 07:53

score 2 · Accepted Answer · answered Aug 25 '17 at 15:38

Time.deltaTime returns the time it took to complete the last frame so it will be roughly constant as you loop through (and a very small value) - which is keeping your up value to remain tiny. You should be able to lerp the value like so.

float t = 0;

void Update()
{
    if (switchOn == true)
    {
        t += Time.deltaTime;
        rend.material.SetFloat("_Blend1", Mathf.Lerp(0, 1f, t/3f)); //3 is time to complete lerp
    }
    if (t > 3) // lerp has completed. reset function and timer.
    {
        t = 0;
        switchOn = false;
    }
}

This worked perfectly. It answered my question by ustilising the Lerp - which seems to be a big help when transitioning. I need to grasp it's uses more. I needlessly complicated it. Thank you again! — Mark Quinn, Aug 25 '17 at 16:32

Changing a shader blend on pointer click over time

2 Answers2