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Setting Shadows Recursively in Unity GameObjects

Want to turn shadows on and off for a GameObject and all its children? I'll show you how.

Created on August 28, 2021. Updated on August 31, 2021.

I wrote an extension method for recursively toggling shadows. You're free to use it! It's relatively straightforward:

public static void SetShadowsRecursively(this GameObject gameObject, ShadowCastingMode mode, bool includeInactive = false)
{
    if (gameObject == null) return;

    var renderers = gameObject.GetComponentsInChildren<Renderer>(includeInactive);

    if (renderers == null) return;

    foreach (var renderer in renderers) renderer.shadowCastingMode = mode;
}

Usage

Copy and paste that code in some utility class. To use it, you can do something like the following:

var parentGameObject = GameObject.CreatePrimitive(PrimitiveType.Sphere);

var childGameObject = GameObject.CreatePrimitive(PrimitiveType.Cube);
childGameObject.transform.parent = parentGameObject.transform;
childGameObject.transform.localPosition = new Vector3(3, 0, 3);

parentGameObject.SetShadowsRecursively(ShadowCastingMode.Off); // No more shadows!

Explanation

Recall that SetShadowsRecursively is an extension method. This is a special type of method that extends an existing class. If you find its first parameter confusing, check out my tutorial on extension methods.

The second parameter is of the type ShadowCastingMode, which comes from UnityEngine.Rendering (make sure you import it!). Remember that this is the parameter:

ShadowCastingMode mode

It's an enum that can be one of four possible values:

The third and final parameter, includeInactive, is optional. It's false by default, indicated by the equals sign followed by false like so:

bool includeInactive = false

includeInactive means to include inactive GameObjects. For example, if you have an object pool of inactive GameObjects whose shadow modes you want to recursively set, this is a necessary parameter. There are other use cases as well.

Moving on, we need to check if the GameObject is null like so:

if (gameObject == null) return;

Returning from a void function in this way is called an early out. I love early outs, and so should you. Using them whenever possible to exit a function keeps your code readable and maintainable.

Next, we get all the renderers recursively with this line:

var renderers = gameObject.GetComponentsInChildren<Renderer>(includeInactive);

The var keyword is a convenience of compile-time type inference. We know renderers is of the type Renderer[], as in an array of renderers, because that is what GetComponentsInChildren is guaranteed to return.

You should know that the name GetComponentsInChildren may be a bit of a misdirect, because it includes components in the parent(!) as well as immediate children, and their children(!), and so on.

You may also be wondering why I chose to get components of type Renderer instead of MeshRenderer. This way it works generically—in addition to GameObjects with the MeshRenderer, the method will apply for those with LineRenderer, and other inheritors of Renderer. (Feel free to modify the method to only affect only specific types.)

Moving on, there is a null check for renderers:

if (renderers == null) return;

Null renderers is possible in an exceptional case. Again, an early out is an acceptable way to deal with this.

Finally, we opt for a single-line foreach block to set each Renderer to the specified mode:

foreach (var renderer in renderers) renderer.shadowCastingMode = mode;

Many people detest single-line expressions, but I find them terse and elegant. Still, change the function to match your sensibilities at your leisure.

Conclusion

Programmers new to C# may find extension methods and optional parameters jarring at first, as did I, but I find them to be fantastically useful language features. Also, Unity's APIs and naming conventions can understandably throw one for a loop (no pun intended). I hope the extension method and/or tutorial helped you!

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