Question Unable to Lerp color of a shared material

Hi there,

I'm trying to have the player character flash red when a projectile collides with them. My idea was to play an animation whenever a collision with a projectile happens. This animation effects a float value that is used in a lerp between two colors.

As the player character is comprised of several primitive 3D shapes that all use the same material and are all parented to the same empty object, I thought to attach a script to the empty object and modify the color of the shared material through the script. This is the script I've used:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Player_Hit : MonoBehaviour
6. {
7.     private MeshRenderer playerMaterialRenderer;
8.     private Color playerColorDefault = Color.cyan;
9.     private Color playerColorDamaged = Color.red;
10.  
11.     private Animator playerAnimationControl;
12.  
13.     public float colorLerp = 0.0f;
14.  
15.     void Start()
16.     {
17.         playerMaterialRenderer = GetComponentInChildren<MeshRenderer>();
18.         playerMaterialRenderer.sharedMaterial.color = playerColorDefault;
19.  
20.         playerAnimationControl = GetComponent<Animator>();
21.     }
22.  
23.     private void OnCollisionEnter(Collision collision)
24.     {
25.         if (collision.gameObject.CompareTag("Swattable") || collision.gameObject.CompareTag("Missable"))
26.         {
27.             playerAnimationControl.Play("Player_Hit", -1, 0.0f);
28.         }
29.     }
30.  
31.     void Update()
32.     {
33.         playerMaterialRenderer.sharedMaterial.color = Color.Lerp(playerColorDefault, playerColorDamaged, colorLerp);
34.     }
35. }
36.  

While the 'colorLerp' float does update as the animation plays, I'm not seeing the material color change at all. As a test, changing out the lerp for this works:

Code (CSharp):

1.     void Update()
2.     {
3.         if (colorLerp > 0.5f)
4.         {
5.             playerMaterialRenderer.sharedMaterial.color = playerColorDamaged;
6.         }
7.     }

The player gets hit by a projectile, the animation plays out, 'colorLerp' value updates and the color changes. However, adding an additional if statement to see if the color can revert after the player was damaged:

Code (CSharp):

1.     void Update()
2.     {
3.         //playerMaterialRenderer.sharedMaterial.color = Color.Lerp(playerColorDefault, playerColorDamaged, colorLerp);
4.  
5.         if (colorLerp > 0.5f)
6.         {
7.             playerMaterialRenderer.sharedMaterial.color = playerColorDamaged;
8.         }
9.  
10.         if (colorLerp <= 0.5f)
11.         {
12.             playerMaterialRenderer.sharedMaterial.color = playerColorDefault;
13.         }
14.     }

This results in the player always being the default color, regardless of whether a projectile hits them.

There's something I'm not grasping here - any help would be much appreciated.

 

There's a lot of extra conditionals in there about which you have said nothing. I would start looking there.

Time to start debugging! Here is how you can begin your exciting new debugging adventures:

You must find a way to get the information you need in order to reason about what the problem is.

Once you understand what the problem is, you may begin to reason about a solution to the problem.

What is often happening in these cases is one of the following:

- the code you think is executing is not actually executing at all
- the code is executing far EARLIER or LATER than you think
- the code is executing far LESS OFTEN than you think
- the code is executing far MORE OFTEN than you think
- the code is executing on another GameObject than you think it is
- you're getting an error or warning and you haven't noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling

Debug.Log()

statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

- is this code even running? which parts are running? how often does it run? what order does it run in?
- what are the names of the GameObjects or Components involved?
- what are the values of the variables involved? Are they initialized? Are the values reasonable?
- are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

You can also supply a second argument to Debug.Log() and when you click the message, it will highlight the object in scene, such as

Debug.Log("Problem!",this);

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

Visit Google for how to see console output from builds. If you are running a mobile device you can also view the console output. Google for how on your particular mobile target, such as this answer or iOS: https://forum.unity.com/threads/how-to-capturing-device-logs-on-ios.529920/ or this answer for Android: https://forum.unity.com/threads/how-to-capturing-device-logs-on-android.528680/

If you are working in VR, it might be useful to make your on onscreen log output, or integrate one from the asset store, so you can see what is happening as you operate your software.

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

Here's an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

https://forum.unity.com/threads/coroutine-missing-hint-and-error.1103197/#post-7100494

"When in doubt, print it out!(tm)" - Kurt Dekker (and many others)

Note: the

print()

function is an alias for Debug.Log() provided by the MonoBehaviour class.

 

As a good practice in general: don't just expose your internal variables to the outside world, it becomes hard for you to track (and debug) what's going on.

Instead make a public method intended for outer services to reach in and do something.
For example if you had

Code (csharp):

1. public float colorLerp = 0.0f;

Do instead

Code (csharp):

1. private float colorLerp = 0.0f;
2.  
3. public void SetColorLerp(float value) {
4.   colorLerp = value;
5. }

And now you might be thinking "pff who needs all this code for something as simple as that" but check this out, you can do this now because you absolutely know that things must go through here.

Code (csharp):

1. private float colorLerp = 0.0f;
2.  
3. public void SetColorLerp(float value) {
4.   if(value < 0f || value > 1f) Debug.LogError("trouble!");
5.   colorLerp = value;
6.   Debug.Log($"value is set to {colorLerp}");
7. }

If that's not handy enough, you can make a property instead of a method

Code (csharp):

1. private float _colorLerp = 0.0f;
2.  
3. public float colorLerp {
4.   get { return _colorLerp; }
5.   set {
6.     if(value < 0f || value > 1f) Debug.LogError("trouble!");
7.     _colorLerp = value;
8.     Debug.Log($"value is set to {_colorLerp}");
9.   }
10. }

You can also check out the call stack for these printouts, and see who the caller was.
Debugging is a huge part of programming, better get used to it.