Lava. In games lava is most often usually done simply as a static river or pool of red liquid. Deadly to step into, but otherwise just a passive barrier to walk around.

Which is weird. Actual lava is an odd substance. It destroys pretty much anything it touches, but at the same time creates land. It is most often flowing, unpredictable, and violent. Sure, there are slow flows on the big Island of Hawaii. But as a game element, how much fun is that? It’s only good as a jump puzzle or perceived danger. So how can something like lava be used in a game world in a more interesting way?

There are two types of lava we will want to play with, basically thick and thin. Thick lava with high viscosity flows slowly and builds up on itself. This type is called A’a’, Hawaiian for stony rough lava.

A flow of A’a looks like, well, stony rough lava. It’s painfully slow but there is inevitability to it. It’s also known to throw out lava balls of up to 20 feet in diameter. Nothing like lava that throws boulders. Already this lava is more interesting than just a barrier obstacle.

Taking it further, what can you the player do to slow this down A’a if it’s making its way towards an inhabited area of the Stygian Abyss? Is there magic that can slow it down? A way to divert the flow to a different place? Rumors of some creatures that live in these types of flows that feed on the matter that the lava consumes? They might not be happy about being diverted away from some rich fertile areas of biological goodies.

The second type of lava are fast flowing rivers of death. This is called Pāhoehoe, for smooth unbroken lava. Really makes you want to live on the big island doesn’t it? This type can move very quickly; in some eruptions it has been clocked north of 120mph. Try running from that.

This type of lava can burrow directly through rock, or creating new rock overnight, such as lava tubes. What kind of new areas could this unlock for the player? Ancient ruins of civilizations from the before times? An undead graveyard? Chances are whatever it is it was buried for a reason.

We look at the ecology of the Abyss as a living thing. This includes a volcano, with the lava flows forming an almost as a living breathing entity, and one that dynamically changes the landscape of the world.

There are challenges when dealing with fluids and games. To do a fully-formed real fluid simulation is very expensive on the processor power. Good thing this is a game and we can cheat some! A simplified approach has been done pretty successfully in some other games for water flow for instance. Minecraft’s water system is cool to play with even though it is not complex. It understands basic flow, and gravity.

Will and Jeff in about a month are going to sort out how we best model lava for our game. This R&D has a bunch of other uses: water, avalanches, oozes, jellies and anything else that may need to follow fluid behavior.
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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.

[...] In most games, burning things have to have particle systems specifically set up for them when the level is built. Like Will’s torch above, the emitter is specifically chosen, sized and positioned to produce a good looking flame that you believe is coming from the torch. Even moving things, like a fireball, have the particle system carefully configured for size and shape and only the position changes during game play. In the Underworld however, where anything that can burn might burn, it would take a great deal of time and effort to set up individual particle systems custom configured to look good for every object. Instead, this week I wrote some code that can make any 3D object look like it is burning without having a custom tailored particle effect.

[...] 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.

With this technology plus the damage system, players will be able to start fires with their fire spells, burn bridges with lava, set creatures ablaze, and generally torch the underworld. Will they use it to solve problems, or create new ones for themselves in the process? That, will be up to them.
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