# zphys

A simple, work-in-progress physics engine written in Zig.

This repository is currently experimental. APIs, structure, and features will likely change as the design evolves.

Status

Early prototype. Expect frequent breaking changes.

Features

Rigid Body Dynamics: Simulation of rigid bodies with basic motion integration.
Collision Detection:
- GJK (Gilbert-Johnson-Keerthi) algorithm for convex shape collision detection.
- EPA (Expanding Polytope Algorithm) for penetration depth and contact normal calculation.
Collision Manifold Generation: Contact point generation for stable stacking.
Primitive Shapes:
- Box
- Sphere
Constraints:
- Penetration constraints solver.
- Friction support.

The project includes several examples to demonstrate the engine's capabilities:

Basic: Simple scene with dropping bodies.
Friction: Demonstration of friction on a ramp.
Pyramid: A stacking demo showing stability.
GJK/EPA Visualizer: An interactive visualizer to step through the GJK and EPA algorithms for debugging and educational purposes.

Prerequisites:

Zig (latest stable). Install instructions: https://ziglang.org/learn/getting-started/

Build all:

zig build

Run tests:

zig build test

To run specific examples, use the -D flags:

Basic Example:

zig build run -Dbasic

Friction Example:

zig build run -Dfriction

Pyramid Example:

zig build run -Dpyramid

GJK/EPA Visualizer:

zig build run -Dvisualizer

Contributions are welcome while we shape the design. Please open an issue or draft PR to discuss ideas and direction first.

This project is licensed under the MIT License - see the LICENSE file for details.