An application that demonstrates the "Doom Fire effect" using Kotlin+TornadoFX
Inspired by Fabien's blog post: https://fabiensanglard.net/doom_fire_psx/
Ideally, after cloning, you should just be able to navigate into the root folder and run the application using gradle:
$ ./gradlew runOnce running, you can press space to toggle the fire source on and off and esc to quit.
The code all lives in a single Kotlin file. It's relatively lean and written first and foremost with the intention of being readable. My recommendation: check out Fabien's blog post linked above first, and then jump into the source file and take a look! The whole thing is less than 200 lines, with a fair bit of it being UI setup that you can just gloss over.
The meat of the algorithm is in DoomFireView#step() which is driven by an
AnimationTimer,
a class provided by JavaFX.
step() updates a buffer which is a 2D array of palette indices (0 being black, 36 being white,
and intermediate indices representing a smooth, fiery gradient that passes through orange/red).
Every time step() is called, each pixel checks the row below it and takes its value, often
decaying into a slightly darker color index (based on a bit of randomness). updateCanvas()
converts those pallete indices into actual pixels on the canvas.
JavaFX requires at least JDK11 (see also: JavaFX getting started). In order to avoid wasting too much time worrying about minimal versions, I just downloaded the latest OpenJDK version (JDK14 at the time of writing this), but you may be able to get away with older versions.
If you see an error like this:
* What went wrong:
java.lang.UnsupportedClassVersionError: org/openjfx/gradle/JavaFXPlugin has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
> org/openjfx/gradle/JavaFXPlugin has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
it means you need to update your JAVA_HOME environment variable to point at a newer version of the JDK.