While working on another project I needed to make some lightweight flames. I looked around, tried a bit of perlin noise, some convolution filters – then some PixelBender filtering – I wasn’t really happy with the results.

I found the excellent Saqoosha’s Fire on Wonderfl.
This demo had nearly the flicker and colour mapping that I was looking for. Rendering the perlin noise on each frame was causing a bit too much processor overhead for my purposes.
Instead of rendering two perlin octaves and moving the layers against each other, I took two separate single octave perlin noise bitmaps and rotated one against the other while blending.
This gives a nice effect and is very lightweight. With the Saqoosha method I was clocking at a steady 26fps, with my lightweight method I could get 90fps.

To get the flame hues I set up a gradient box, threw some colours at it, loaded those colours into an array which I then pushed to a palette map.

So how to use the Flamer class:

import swingpants.effect.Flamer

var flamer:Flamer=new Flamer(display_object)
addChild(flamer)

addEventListener(Event.ENTER_FRAME, enterFrameHandler)
function enterFrameHandler(event:Event):void
{
flamer.update()
}

Your object will now be on fire. Feel naughty?

You can set the render width and height and also set the direction of the flames by setting a point vector.

var flamer:Flamer=new Flamer(display_object,render_width, render_height, flame_direction_point)
addChild(flamer)

//The colour of the flames can be set with one of the presets (There are 4 at the moment – ORANGE_FLAME, BLUE_FLAME, YELLOW_FLAME, GREEN_FLAME – but I will be adding more)
flamer.setFlameColour(Flamer.BLUE_FLAME)

//Direction can be set on the fly:
flamer.setFlameDirection(direction_point)

Here is a demo of a pure code use of the Flamer: The Flaming Vortex. You can click on the flash to initiate an explosion, and pressing space will change the colour. Have a play:

Flamer Class. The flaming vortex demo

This next demo is an example of throwing a movieclip/sprite at the Flamer class. Don’t laugh, I quite literally spent 10 minutes putting the anims together then threw them at the Flamer. Click on Flash to change colour and object.

Flamer Class Demo. Help, my car is on fire

Lots of fun can be had by throwing different animations at the Flamer. Control some with your mouse/keys. Become a twisted fire starter.

The Flamer class could do with a few more features, but is a pretty good start. The speed is pretty good, I’m happy to receive any improvement recommendations.

I have packed the Flamer class and demos up in a zip if you want to have a play:
DOWNLOAD: Flamer Class and Demos

DEMO #1: Flaming Vortex
DEMO #2: Burning Movieclips

#1 Put your gradient mask on the stage – lets call it gmask
#2 Put the object to be masked on the stage.
#3 Set both the mask and the ‘object to be masked’ to cacheAsBitmap
#4 Apply the mask to the object

In #AS3
gmask.cacheAsBitmap = true
obj_to_be_masked.cacheAsBitmap = true
obj_to_be_masked.mask =gmask

In #AS2
gmask.cacheAsBitmap = true
obj_to_be_masked.cacheAsBitmap = true
obj_to_be_masked.setMask(mask)

It really is as simple as this.
Note to designers: Gradient masks can’t obviously be done directly from the IDE (see below), but these three lines can be placed on the timeline if so desired.

To put a gradient mask on dynamic text you will need to place the text within a container (movieclip/sprite) and mask that.

The object to be masked can also contain animation, text or video though this will require a bit more processor as the bitmap will need to redraw on each frame. Often this is well worth it as the effect can be great.

There is a way of achieving this same effect with no code at all and here it is:

#1 Put your gradient mask on the stage – lets call it gmask
#2 Put the object to be masked on the stage.
#3 Put both of these items into a movieclip/sprite (the container) making sure the mask is on a layer above the object
#4 Give the mask a blend mode of ‘Alpha’
#5 Give the ‘container’ a blend mode of ‘Layer’

And there you have it. Gradient masking achieved with blendModes and absolutely no code.

Benchmarking the two gradient mask methods:
I used each method to mask an embedded video – then placed an instance on the display list and ran at varying frame rates.
Initially there was negligible difference between the code and blend mask methods. I ramped up the FPS to 120 and put four instances of the video on screen. With this set up the code method (cacheAsBitmap) was up to 4% faster than the blendMode Mask method.

Conclusion: The code method is faster but very marginally. If you are desperate for a bit of extra juice go with code.