Method of returning light value of particular point?


I am very new to both C++ and Unreal Engine 4 and am have begun work on a project requires me to either develop of find some ways of telling how much light from a particular light source is hitting an object. For example, say the light from my directional light is being cast onto Object1, causing Object2 to be in its shadow. What would be some ways of telling which objects are being lit by that particular directional light? Also, is it possible to retrieve some form of scalar value rather than a boolean telling me whether or not a collision has occurred (as you would encounter when ray-casting).

If anyone could give me some pointers here it would be greatly appreciated. If more information is required I am happy to discuss furhter :).

Thank you.