mandlebrot_explorer

Purpose:

The purpose of this program is to be an easy to use fractal explorer and a demo of interactivity using the SDL2 library.

Dependancies:

To install this program, one must have SDL2 (available from their website or most package managers) and must have a compiler that supports OpenMP. Additionally, one needs CMake to run the build scripts.

Compile & Install:

Tested on POSIX, but Visual Studio should be able to import the CMake File.

mkdir build && cd build && cmake .. && make

You can then run the program by running the generated executable build/mandlebrot_explorer

Usage:

Run the program, you can then use the:

Left Click to recenter the fractal on the mouse

arrow keys to coarse pan

hjkl to fine pan

+ / - to coarse zoom

y / u to fine zoom

[ / ] to increase or decrease the amount of iterations done. Decreasing the iterations reduces sharpness but greatly speeds up rendering. It could be nice to allow the image to be blurry while you find an area of interest, speed drawing, then sharpen for desired effect

i / o increases or decreases the amount of modulo blending. This is crucial to get things to look coherent at different zoom levels.

m toggles to 'modulo view'

n toggles to 'histogram view'

Numbers 1 - 4 allow you to toggle between preloaded color maps from src/config.cpp (from this repo 1 and 2 are loaded with data, 3 and 4 are not).

r to reset your view and scale back to the main fractal

p to print the current state, to replicate it

q to quit

t to pull up the controls menu

All printing statements will show up on the terminal you used to call the program, but effort will be made to made interactions more graphical.

Customization:

To customize, copy src/config.cpp.def into src/config.cpp and make your edits there, then rerun the above build commands. Note that running make clean will delete your custom src/config.cpp file

src/config.cpp is in the .gitignore, so you can edit without worrying about syncing with the repo.

However, beware when you pull if there are changes that will cause your src/config.cpp to become incompatable.

In the file, you can modify the color palette, num threads, pixelWidth, etc.

It should be fairly self explanatory.

TODO / BUGS:

More intellegently setup a color gradient for historgram. Now histogram looks great at some zoom levels but garbage at others. Also more intellegent "bucket" placing for histogram
More intellegently split work between threads, rather than having each take a stripe. Maybe guess where the most work would need to be done?
Have a better interface to scroll multiple steps at once, perhaps click and drag and/or boxes to type in Xmin/Xmax Ymin/Ymax
Add GUI elements to ajust the colormap
Add a second window as a "HUD" to show where you are on the fractal
Investigate bug where at high zoom levels thread panes get out of sync
Take advantage that panning reuses many existing pixels to not recalculate everything
Since a recent SDL patch, seems to now run over 100x slower on MacOS (seems fine on linux though), may need to use a different API call.

Examples Images

Depending on what you are looking for, both the Historgram and Modulo renderings can look nice.

However, the Modulo rendering tends to be more consistently nice. It also has zoom invariance

The Histogram renderings are a bit finicky in my experience. It tends to look very nice on certain structures and confused on others. Playing with the gradient, and how much automtic vs manual shading can give you some interesting results.

Here are some comparisons. Look closely at the ring around the mandlebrot itself. The modulo's tend to show more detail at the cost of looking bust or almost messy.

By Contrast, around spirals or areas where the set is very thin (little black), the histogram coloring can look very nice.

Modulo:

Histogram: