https://infinifractal.hilarylau.io
A Mandlebrot set fractal viewer in C++. Continuously deployed and ccessible through the browser using Emscripten.
The graphics is handled by SDL2. On every rerender, we lock the pixel buffer, update all the pixels with the new colors, and then unlock it.
For the calculation of the iterations under the Mandlebrot scheme, we set the divergence limit to be 2.0 and count the iterations. The maximum iterations we allow is 500 for performance issues. However, integer iterations cause banding in the colors. Therefore, we use a interpolation formula as described in this article that allows for fractional iteration estimates, since the number of iterations under the scheme is actually continuous.
Previously, there was a bottleneck in the program due to the rounding performed while converting from HSL to RGB, which caused color banding. To prevent that, we created a function that cycles through colors directly in RGB using a sine function and appropriate phase shifts for each color.
We also implemented WebAssembly support through index.html, with proper thread usage. Since browser resources are much more limited, we only allow 150
maximum iterations of the Mandlebrot scheme, which may decrease the quality of the resultant image. Moreover we implemented a progressive loading
scheme where we first render a low resolution pass of the frame, and then increase the resolution progressively.
The original implementation is single threaded, naively rendering one pixel at a time. The draw time of a single frame is around 5000ms.
The current version parallelizes the process using a threadpool implemented in Threadpool.cpp. Each horizontal line of pixels is handled by a separate thread.
With threading, the draw time of a frame is around 925ms, indicating a 5.4x speedup over the single threaded version.
- Hardware acceleration like CUDA could potentially allow for performance improvements
- We might want to avoid manipulating pixels directly for performance
Depends on SDL2. Run brew install sdl2.
To install, run make and then the application can be started by running ./infinifractal.
If you want to run this on a browser using WebAssembly, run make wasm and then ./corsserver.py to serve the files with the correct CORS headers. Then
access localhost:8000 to see the fractal.