= Assignment 2 Discussion and FAQ =

== Question 1. Dealing with 'const' ==

Pbrt's {{{Primitive}}} interface defines the {{{Insersect}}} and {{{IntersectP}}} methods as {{{const}}} methods. However, your lazy K-D tree needs to modify internal structures as it builds out the tree as part of the implementation of these methods.  The easiest solution to this problem is to declare all members of your lazy K-D tree class that get updated in these methods as {{{mutable}}} structures.  In C++, mutable class members can be modified by const methods.  For example, if you wanted a mutable integer {{{foo}}}, you'd declare it as:
{{{
mutable int foo;
}}}