After working like mad on the book, I have been squeezing in time to continue tweaking my particle system demo. I think it is fairly close to being finished now... I made a simple texture to apply to the particles, and use additive blending to write them onto the render target. The rules of the particle system are gravitationally based, with one point being an emitter and one point being a very massive object (i.e. gravitationally 'impressive' [grin]). The system runs quite well on the GPU, with many, many particles on screen at the same time. The following image sequence demonstrates what the particle system does with a particular value for the mass of the attractor. The particles are colored based on the distance from the attractor:
Thus far I am happy with the results, and will only perform smaller tweaks to the demo in the near future. I may make a few more parameters in the system adjustable at runtime to allow the user to interact a little bit more, but I need to wrap up a few more book related items before the end of the year (so time will be tight...). We'll see how much further I can get before my 'end of year' post [grin]!