I built a real-time simulation of a supermassive black hole with two orbiting stars, using ray tracing for gravitational lensing effects (Schwarzschild metric). It features OpenGL/GLSL rendering, a deformed spacetime grid, an accretion disk, and interactive camera controls.

Inspired by this YouTube video: https://www.youtube.com/watch?v=8-B6ryuBkCM (done in C++), I reimplemented it in pure C.

Here the source code: https://github.com/mrparsing/C-Projects

This has been my biggest project in C and Systemverilog so far and very rewarding after nights of grinding.

Although the source code is compiled as C++, the code I wrote for the RISC-V is just using C features.

The cpu runs at 25Mhz, RAM 32 KBytes and framebuffer of 64 KBytes. As a result, I am displaying a GIF of 195x146, 12 bit color, at ~4FPS

I used memory mapping to talk to the different peripherials basically. Given that there is not much RAM available, I couldn't use standard library, and had to implement some functions myself like memcpy and println.

Link to the software (AnimatedGIF and RISC-V example): https://github.com/martinKindall/AnimatedGIF/tree/riscv_port/examples/riscv-32i

Link to the HDL: https://github.com/martinKindall/risc-v-single-cycle/tree/gif_player

Thanks to:

AnimatedGIF maintainers

ZipCPU maintainers, link to their qspi driver: https://github.com/ZipCPU/qspiflash/blob/master/rtl/qflexpress.v

Trees loop through a short loop.

Path and sky is random (10 % sky has a star and 1% chance of being a shiny one).

Bottom text loops through a short conversation.

Ray-marched 3D rendering in ASCII/Unicode. Made for fun.

C11, includes lighting, weather effects, and audio.

https://github.com/Lallapallooza/c_ascii_render/tree/main

source code: https://github.com/formodx/parallax

So far, I've spent about 4 months programming the emulator. It's been usable for the last 2 months. By default, it is in its cycle accurate mode with the slower but more accurate APU mixer.
Supports mappers 0, 1, 2, 3, 4, 7, and has basic gamepad support for up to two players.

Video: Cosmic structure formation, with 2 million (128³) particles (and Particle-Mesh grid size = 256³).

Source code: https://github.com/alvinng4/grav_sim (gravity simulation library with C and Python API)
Docs: https://alvinng4.github.io/grav_sim/examples/cosmic_structure/cosmic_structure/

In my opinion, progress bar is one of the most important element for user interface. Yet, I failed to find any good progress bar library for C. So, I wrote one myself so that I could use it for my simulation programs. I hope this could help any of you in your projects.

Note that this is a very simple implementation, inspired by rich.progress in Python. Feel free to fork it and build your own version if you like to.

Source code: https://github.com/c-modules/c_progress_bar