Unity’s LayerMasks: How do They Work?

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LayerMask: How it Works?

LayerMask specifies a set of layers contained with a technique called bitmasking, which allows a bitchain to use each bit as a value (e.g., a data type of 4 bytes can have )

Unity has the first 8 layer values specified ()

As I explained in a Game-Dev Stack Exchange question, there is a lack of good documentation on Unity’s side and people (including me at the time) tend to get confused with the values that we should assign to GameObject’s layers.

When a LayerMask evaluates if it contains a GameObject’s layer, it uses something similar to the function HasLayerValue declared in the following code snippet:

public static class LayerMaskExtensions
{
	public const int LAYER_DEFAULT = 0;
	public const int LAYER_TRANSPARENTFX = 1 << 0;
	public const int LAYER_IGNORERAYCAST = 1 << 1;
	public const int LAYER_WATER = 1 << 3;
	public const int LAYER_UI = 1 << 4;

	/// <summary>Evaluates if Layer Value is in LayerMask.</summary>
	/// <param name="mask">LayerMask to evaluate.</param>
	/// <param name="layer">Layer to evaluate if it is contained in LayerMask.</param>
	/// <returns>True if value is in LayerMask.</returns>
	public static bool HasLayerValue(this LayerMask mask, int layer)
	{
		return ((mask | (1 << layer)) == mask);	
	}
}

 

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