Fire and Smoke in After Effects (Part I)

By: Tiago Dias

Tiago Dias works at a corporate television and news production company based in London with subsidiaries around the world, as a video producer and Flash developer — this is Tiago's ideal job, as it combines 2 of his favorite technologies! In his free time he writes tutorials on Flash and After Effects for various communities.

The question I get most nowadays is: How do you create Fire & Smoke? What are your little hints for accomplishing it? Should I use a plug-in or go with the built-in effects? This tutorial will show you how to create Fire & Smoke with only the bundled plugins that you get when buying the Pro Version of After Effects 7. In case you are using the standard version, you can download a trial of Cycore Cult Effects from their website.

Fire & Smoke in After Effects

Before we even start, do some experiments to see how fire reacts to different physics and how smoke reacts/moves.

(Please experiment in a safe location outside your 4 walls.)

Below is a screenshot of the effect we are about to create:


Figure 1Car burning

Before I started to write this tutorial I was thinking: What should I set on fire? I came up with a few ideas such as a car, a match, a tree, a newspaper. In the end I went for the car. That's where our tutorial starts.

I've found this picture of an old car somewhere in the woods by simply searching Google's picture search site.


Figure 2 – Car image

There is a lot of stuff which we need to remove so we get a clear view of the effects that we are creating. I've opened this image in Photoshop, and with the lasso tool I've removed the inside of the window. I've also made the top of the car transparent.


Figure 3 – Edited car image

Why are we doing it this way? The transparent parts of the image will be recognized as Alpha Channels in After Effects.

An Alpha Channel is the opacity channel of an image or video footage. If a pixel has a value of 0% in its alpha channel, then it becomes transparent. This way you can put other pictures behind or in front of another.

When you're done with removing the window and top of the car, create a folder for this project and save the car image as a Photoshop file named old_car.psd.


Creating the Smoke

  1. Open After Effects and create a new Project called Fire&Smoke.
  2. Save the After Effects Project file to the same directory as your Photoshop image.
  3. Create a new Composition called Smoke 1 with the following settings:
    • Width: 200px
    • Height: 350px
    • Pixel Aspect Ratio: Square Pixels
    • Frame Rate. 25fps
    • Duration: 14sec

      25fps is the normal frame rate for the PAL standard, other countries like North America use 30fps which corresponds to the NTSC standard.

  4. Create a new Solid by right-clicking on the timeline window and selecting New -> Solid CTRL + Y. or by pressing
  5. Name this new solid smokeBase and ensure that the size matches the composition height & width by clicking once on the "Make Comp Size" button. I've chosen Black as Background color, when you apply the Particle Playground effect the Background Color of the Solid will become transparent.


    Figure 4 - New composition window

  6. Select the newly created solid and press the F3 key to open the Effect Control panel. In the Effects & Presets menu (Control + 5, or, Window > Effects and Presets) twirl-down the Simulation settings options and double-click the Particle Playground effect.

    You will notice a whole bunch of settings in the Effect Control panel, but don't be scared, I will help you through the whole effect.

    Press the play button in the Time Controls panel, or 0 on your numerical keypad to preview the effect.

So where are the particles? I'm just seeing two red dots. Particles are supposed to grow, so if you scrub to the middle of the timeline you will see a bunch of red dots flying around. Those are our particles that we'll change to smoke in the next few steps. Below you see a screenshot of the particle through the timeline


Figure 5 - Particles over time

This doesn't really look like smoke, these are just some red dots flying around. What should I do with this? Well, have no fear, help is here...

First let us change some settings for how the particles grow and appear on the screen. Twirl down the Cannon Properties in the Effect Control panel and change the following settings:

  • Barrel Radius: 30
    The radius of the particle grow, higher numbers result in much wider particle grow space, low numbers create a geyser like particle explosion
  • Particles per Second: 120
    Number of Particles generated per second
  • Direction: 0x+8.0°
    (We want to have the smoke slightly tilted to the right
  • Direction Random: 38
    Lower values results in a straight jet, higher values creates that randomness which we're looking for
  • Velocity: 70
    the standard value is too fast for smoke, we can also lower it even more to create "heavy" smoke, but 70 fits best for this project
  • Velocity Random: 135
    here for we want to have a more wild particle spray, to create a more realistic look
  • Color: #4F4F4F
  • Particle Radius: 3.5

When you're done with these settings, you may want to play around with them to get a real feeling for the effect.

One property we didn't change is the Position value. Let's move it to the bottom of the comp: 100, 384 (the first value is the width position; second the height position of the Particle generator.

On a side-note, there are occasions where the Particle generator is called Producer or Particle Producer

If you scrub the playhead you will just see a small portion of the red dots at the bottom of the composition. That's alright, we are going to change a few other values to make our smoke act in a more natural way then at the moment, the dots are just being sprayed up and falling down again.

Let's twirl the Gravity property and change the Force Value to 0. If you do a quick render or scrub the playhead, you will see that the particles are flowing upwards to top edge of the composition.

6

Figure 6 – Particles flying upwards

But this still doesn't look like smoke to me...

The next step is kind of a nifty trick to create quick & dirty smoke ;)

With your smokeBase Solid still selected, apply a Fast Blur Effect from the Effects & Presets > Blur & Sharpen group. Assign a Blurriness value of 15, and leave the other settings as they are. Preview your comp. Now this looks a lot more like real smoke, don't you think so?


Figure 7 – Smoke


Continue to... (Part II)

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source:http://www.communitymx.com/content/article.cfm?page=4&cid=1A9CF

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