Creating a brush fire emitter

Sunday, 3, March, 2002 at 10:49:55 PM

While Illusion has the potential to be used for an unlimited number of effects, the two most common effects new users want to create are smoke and fire. While a smoke emitter can be very simple to create, a good fire emitter can take much longer. Here's my recipe for a brush fire effect, which was also used as a torch effect in my short film "The Legend of Wunday".


The first step in creating a fire emitter is choosing an emitter shape that won't look too obviously like an emitted shape. I created a series of "Rice Grain" shapes, ovals with a bit of noise and holes in them to break up the repetitiveness. Add the new shapes, click on Random Start Frame, and turn the Frame speed slider from fast to off.  Rather than having each particle cycle through the shapes as a series, these settings assign a random particle shape from the series to each new particle  for it's entire life. Next, switch the Particle Angle to Random.

Click here to download the Grain fire particle shapes (36kb zip)

In Colors, choose a series of deep reds, browns, tans and golds,starting with the lighter colours, and ending with browns and reds which are close to black. In transparency, uncheck the Link Transparency to Color option, and set a black at the start, white not far after that, then a second white at about the 80% mark, and a second black at the very end, so that each particle fades in and out. Also, make sure the Intense option is selected at the top of your particles tab.


Now for the Particle type options. The Life parameter should be set halfway between min and mid. For Size and Velocity, set the level at the mid point. Set the particle Weight to -max, so that the particles start to float upward. Then turn the particle Number all the way to max. Now hop into your Emitter Properties and turn your Emitter Range from 360 to 0, and the emitter angle from 0 to 90. This should give you a pillar of fire type effect.

We can add some randomness by playing with the variation settings. Life Variation should be pushed up about 3 notches, somewhere close to the first grey line. Number, Size, and Weight Variation should be around the second grey line, about halfway between min and mid. Motion Randomness and Velocity Variation should be just a few notches below mid, and Spin Variation should be all the way up to max.

The Over Life settings will add a little more jump to the fire. The most important of these settings is to add a lot of difference in the Velocity over Life setting. This causes the flames to leap around a bit, and improves the overall random look.

Next, the Size over Life settings will add a little bit of a point to the flames. Set your control points in a bottle shape, starting at a high range of roughly 160, and ending with a size of about 50.

The Weight over Life setting could be adjusted so that the particles get lighter as they ascend.

And that's a basic fire effect! To add some more detail, I suggest copying the particle type (by clicking on the New particle type button while the particle is selected) and adjusting some settings to add a "gasiness" to the fire. By turning off the intense option, increasing the size of the emitter shapes, and changing the whites to a mid grey in the transparency settings, a smoky gas look can be achieved (you may also need to make sure that the Keep particles in order setting remains unchecked). Both "spark" and smoke particle types can be helpful in adding some realism to the fire as well.