The latest Kickstarter update from OtherSide Entertainment is all about lava…and particle systems:

We want the world of UA to react as much as possible like the real world to such events, which means making anything that should be able to catch on fire, actually able to catch on fire. There are two parts to this. One is the logical level… how do things catch on fire and how does that fire burn other things. That gets into a general damage system, which is something I’ll write about more in the future. The second part, though is making burning things look like they are burning. I put some time in on that this week and have had some promising results.

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Particle systems have become more sophisticated over the years, but the technique is still basically the same. A particle system is an optimized render of a whole bunch of little tiny polygons or “particles”. Each particle is obeying a set of very simple physics rules to move it every frame. Anything that moves like a fluid is well represented by a particle system. Smoke, fire and fog are all things that particles represent well. The NVidia examples of water and fluid Chris shared last week are also particle systems, just made up of a lot more particles packed a lot more densely.

A good looking fire typically has orange and red particles for the flame itself as well as grey particles to simulate the smoke.

You can see a sample image of a torch flame above; this is something that one of OtherSide Entertainment’s people has been working on recently.

To make an object seem to burn, I need to create fire particles at the surface of that object. The surface of any object is defined by one or more meshes of triangles, so those meshes become my emitters. The process for creating each particle goes like this:

1. Randomly choose one of the burning object’s meshes.

2. From that mesh, randomly choose one of its triangles.

3. Randomly choose a point somewhere on that triangle.

4. Tell the particle system to create a particle there.

The end result, as you can see in the little movie below, is flame (or any other particle effect) that seems to come from the surfaces of the object. The randomness makes it dance around, coming from different parts of the object moment to moment, much as a real fire would.

You can click on through to see a video of some of their fiery particle systems in action.

Oh, and if you haven’t yet filled out your BackerKit survey for Underworld Ascendant, please do so. If you haven’t received your BackerKit email from OtherSide Entertainment, and if you backed Underworld on Kickstarter…hopefully you haven’t cleared your spam folder in the last couple of weeks.