Implementing a volumetric explosion

The art of game development is a clever trade-off between realism and efficiency. This is particularly true for explosions; they are at the heart of many games, yet the physics behind them is often beyond the computational power of modern machines. Explosions are, essentially, nothing more than very hot balls of gas; hence, the only way to correctly simulate them is by integrating a fluid simulation into your game. As you can imagine, this is unfeasible for a runtime application, and many games simulate them simply with particles. When an object explodes, it is common to simply instantiate fire, smoke, and debris particles so that together they can achieve believable results. This approach, unfortunately, is not very realistic and is easy to spot. There is an intermediate technique that can be used to achieve a much more realistic effect: volumetric explosions. The idea behind this concept is that explosions are not treated like a bunch of particles...