Fuel -- Deeper explanation and how to make an object catch fire from another

[davision]

I'm really having a hard time understanding what the Fuel channel does and more importantly, how it should be used.

In my mind, when talking about fire -- fuel is some coals, or maybe a piece of wood which is initially ignited to then converted into heat and light energy (fire).

When I visualize the 'fuel channel', I'm seeing something resembling smoke. This doesn't seem like "fuel" to me (it isn't very wood-like), and that's why I don't understand the term's usage in Phoenix.

Here is an example of what I'd like to do -- I think it would be very educational for me...

I would like to know how to set up a simulation in which a wood log (a cylinder placed at a 45 degree angle let's say) will begin burning from the lower end and the fire will propagate up to the other end of the log. I don't want to do this using an animated map, but through Phoenix's own natural propagation.

Secondarily, I'd like a second log (a cylinder positioned vertically above the higher end of the first log) to be shown initially dormant. I would like to see that second log 'catch' fire as the flames propagate up the first log.

Based on what I've read in the documentation, I don't have the slightest idea on how to set this up.

Please, someone, describe the basic procedure, or even supply a sample file. I would be most appreciative.

[Ivaylo Katev]

your observation is correct, the fuel in phoenix is a gas (or liquid), not a property of the rigid bodies. actually there are some ideas to introduce materials for the rigid bodies, that will allow to control the friction for example and eventually the fuel/heat properties. however, this is not a reality yet and you have to fake the effect via animated texture. you can try to use the gaseous fuel, but its propagation speed is relatively fast compared to propagation of the fire in a log. even if you decrease the propagation to zero, i thing it will be faster than the needed one, but try it.

[davision]

I don't need the propogation speed to be slow -- that was just an example. I just want to know how to set up a scene where the fire starts in one place (the low end of log) and then travels along that body and then catches another object on fire. I just want to know how that can be done (without animated textures).

[Ivaylo Katev]

ah ok, see the "propagate" scene, it shows exactly this. the burning fuel produces heat, this heat ignites the near-by fuel and etc...

[davision]

Aha, I didn't know there was a propagate sample. I had only read through the samples listed in the docs.

The sample is pretty cool. I guess the included script is designed to create that static 'box' of fuel -- is that right?

Is it possible to create a stationary fuel area any other way? I tried using a box with it's source helper set to 0 velocity, but the fuel gets 'stirred' into the surrounding air pretty quickly.

[Ivaylo Katev]

yes, the script is to create the fuel. you can use a geometry source in brush mode instead, just include the geometry in the exclude list and set it to produce fuel.

[davision]

The brush method sounds simpler. Why did you use the script instead of brush mode in the example? Does it offer some advantages?

[Ivaylo Katev]

i'm a programmer, for me the script is easier