Uses of layers in Unity

You can use layers to optimize your project and workflow. Common uses of layers include: * Layer-based rendering. * Layer-based collision.

Use the Camera culling mask with layers.

You can render only the objects in a particular layer, or selection of layers, if you use the Camera’s culling mask . To change the culling mask, select the camera you want to use, and select the Culling Mask dropdown in the Inspector window. If you clear the checkbox of a layer, it doesn’t render in the scene.

Note: UI elements and screen space canvas children are exceptions to this and render regardless.

Ray cast with layers

You can use layers to specify which GameObjects that a ray cast can intersect with. To make a ray cast ignore a GameObject, you can assign it to the Ignore Raycast layer, or pass a LayerMask to the ray cast API call.

If you don’t pass a LayerMask to the ray cast API call, Unity uses Physics.DefaultRaycastLayers which matches every layer except Ignore Raycast.

The Physics.Raycast function uses a bitmask, and each bit determines if a layer is ignored by rays or not. If all bits in the layerMask are on, the ray collides against all colliders. If the layerMask = 0, there are no collisions.

For example, if you want to cast a ray on layer 8, see the code sample below:

int layerMask = 1 << 8;

// Does the ray intersect any objects which are in layer 8?
if (Physics.Raycast(transform.position, Vector3.forward, Mathf.Infinity, layerMask))
{
    Debug.Log("The ray hit the player");

You can then do the inverse, so that the ray collides with all layers except layer 8.

void Update ()
{
    // Bit shift the index of the layer (8) to get a bit mask
    int layerMask = 1 << 8;

    // This casts rays only against colliders in layer 8.
    // But to collide against everything except layer 8, use the ~ operator because it inverts a bitmask.
    layerMask = ~layerMask;

    RaycastHit hit;
    // Does the ray intersect any objects excluding layer 8.
    if (Physics.Raycast(transform.position, transform.TransformDirection (Vector3.forward), out hit, Mathf.Infinity, layerMask))
    {
        Debug.DrawRay(transform.position, transform.TransformDirection (Vector3.forward) * hit.distance, Color.yellow);
        Debug.Log("Did Hit");
    }
    else
    {
        Debug.DrawRay(transform.position, transform.TransformDirection (Vector3.forward) *1000, Color.white);
        Debug.Log("Did not Hit");
    }
}

Note: If you don’t pass a layerMask to the Raycast function, it still ignores colliders that use the IgnoreRaycast layer.