buddhabrot-go

A Buddhabrot plotter written as a Go, React, and TypeScript learning exercise.

This plot took about a minute on an eight-core machine.

Usage

Set the MySql Password

You'll need to the MySQL root password. Create a file in the root of the repository called .env and set the contents to DB_ROOT_PASSWORD=yourchoice.

Run It

In the same directory run docker compose up, which starts the web application on http://localhost:8000.

Request a Plot

The form on the left of the app defines the parameters that are used to plot an image. The table on the right shows the plot history and links to images of completed plots. Click the plot button to enqueue a plot.

Under the Hood

The parameters used to plot the image are posted to an API running on port 3000, and the API records them in the database. The row ID returned will be used to obtain a PNG image of the plot after it is complete. Because the plotting is CPU intensive, RabbitMQ is used to enqueue the plot request for a separate plotter process so the API request doesn't block.

A sample plot request:

{
    "sampleSize":100000000,
    "maxIterations":5000,
    "region": {
        "minReal":-2.0,
        "maxReal":1.6,
        "minImag":-2.0,
        "maxImag":2.0
    },
    "width":512,
    "height":512,
    "gradient": [{
            "color":"#000000",
            "position":0.0
        }, {
           "color":"#ff8000",
           "position":0.5
        }, {
           "color":"#ffff00",
           "position":0.75
        }, {
            "color":"#FFFFFF",
            "position":1.0
        }
    ],
    "dumpCounterFile": false
}

If put in a file called params.json, it could be posted with:

curl -Ss -d @params.json -H "Content-Type: application/json" \
    http://localhost:3000/api/plots

This is included in the samples directory in a file named plotrequest.sh along with the JSON file above, so to test the plotting you can run:

./request.sh

You will get a response similar to this; note the Id property.

{
    "Id": 25,
    "Plot": {
        "SampleSize": 10000000,
    ...

Getting Images

Given the Id from the previous step, you can do a get to /api/plots/25. If the plotter process has completed the plot, this will return a PNG image. Otherwise 404 is returned until the plot is complete. To do this with curl:

curl -Ss "http://localhost:3000/api/plots/25 > image.png

A script for this is also included in the samples directory and can be run as:

./getimage.sh 25 > image.png

Parameters

For a thorough explanation of the Buddhabrot see Wikipedia's page here.

Parameter	Description
sampleSize	The number of random sample points not in the Mandelbrot set.
maxIterations	The maximum number of orbits per point.
region	Defines the complex plane region points are sampled from.
- minReal	Minimum real component for each point.
- maxReal	Maximum real component for each point.
- minImag	Minimum imaginary component for each point.
- maxImag	Maximum imaginary component for each point.
width	Width of plot image in pixels.
height	Height of plot image in pixels.
gradient	Array of "stops" which are used to color the plot.
- color	Hex color of the stop.
- position	Position of the stop in [0, 1].
dumpCounterFile	If true, dump the orbit counts per pixel to a file called counter.txt in the log directory.