In C#, when you do
Class(Type param1, Type param2) : base(param1)
is the constructor of the class executed first, and then the superclass
Your question is a bit unclear but I'm assuming you meant to ask the following
When to I call the base constructor for my XNA object vs. using the impilict default constructor
The answer to this is highly dependent on both your scenario and the underlying object. Could you clarify a bit wit the following
TerrainCollision
?My best answer though is that in the case where you have parameters that line up with the parameters of the base class`s constructor, you should almost certainly be calling it.