An extension class for Unity Renderer that checks if it's seen from a specified camera

RendererExtensions.cs

using UnityEngine;

public static class RendererExtensions
{
    /// <summary>
    /// Checks if the object is visible from a certain camera
    /// </summary>
    /// <returns><c>true</c>, if visible, <c>false</c> otherwise.</returns>
    /// <param name="renderer">Object Renderer</param>
    /// <param name="camera">Camera</param>
    public static bool IsVisibleFrom(this Renderer renderer, Camera camera)
    {
        Plane[] planes = GeometryUtility.CalculateFrustumPlanes(camera);
        return GeometryUtility.TestPlanesAABB(planes, renderer.bounds);
    }
}