To make particle explosions look really good, simulating natural phenomena like fire or flowing liquids, we need to implement a blur algorithm. In this tutorial we'll implement a straightforward version of the "box blur" algorithm. If you want to really practise your C++, implementing blur algorithms is a good way to do it. I won't optimise the algorithm in this tutorial -- I'll leave that as an exercise for you. But provided your computer is reasonably fast, the implementation I demonstrate here will do the trick.