A single-file 2D collision library written in C.

The goal with this library is to create a straightforward library that checks for collisions and calculates overlaps for a wide variety of 2 dimensional shapes and lines (and doesn't try to do anything else). It should be clear from the code and the comments what each function is doing.

SIMPLE_COLLISION_2D_IMPLEMENTATION should be defined in one C/C++ source file before including this header. It can then be included in any other source file that references its functions like a standard header.

The sc2d functions all follow a similar structure and all return true if a collision has occurred.

bool sc2d_check_shape1_shape2(
	[in]  float p1x, 
	[in]  float p1y, 
	[in]  float shape1_dimensions ... ,
	[in]  float p2x,
	[in]  float p2y,
	[in]  float shape2_dimensions ... ,
	[out] float *overlap_x,
	[out] float *overlap_y,
)

There are no dependencies aside from math.h by default. To eliminate this, define your own replacements before including the implementation code.

#define sc2d_hypotf hypotf
#define sc2d_fabsf fabsf
#define sc2d_min fminf
#define sc2d_max fmaxf
#define sc2d_atan2 atan2

#define SIMPLE_COLLISION_2D_IMPLEMENTATION
#include "sc2d.h"

The overlap vector is always relative to the first shape in the argument list. Therefore, for static resolution it should be subtracted from the position of shape1 and/or added to position shape2 to push the shapes apart.

if (sc2d_check_circles(p1.x, p1.y, r1, p2.x, p2.y, r2, &overlap.x, &overlap.y)) {
	p1.x -= overlap.x / 2.0f;
	p1.y -= overlap.y / 2.0f;

	p2.x += overlap.x / 2.0f;
	p2.y += overlap.y / 2.0f;
}

By default, the polygon collision functions sc2d_check_poly2d and sc2d_check_point_poly2d assume vertices are defined as float x/y pairs. To use these functions with a different type, you can define a custom sc2d_v2 struct type with members x and y before the implementation as follows:

#ifndef SIMPLE_COLLISION_2D_VECTOR2
typedef Vector3 sc2d_v2;
#define SIMPLE_COLLISION_2D_VECTOR2
#endif

#define SIMPLE_COLLISION_2D_IMPLEMENTATION
#include "sc2d.h"

The demo project uses Vector3 in this way (z is ignored) to demonstrate this. This may or may not be a good idea.

The included demo program currently uses raylib version 4.0.0 or later, but doesn't make extensive use of its features. Set sc2d_RAYLIB_DIR in src/demo/CMakeLists.txt to a raylib source directory on your machine.

Also included is a build/run configuration for Windows.

config.bat
build.bat
run.bat

This assumes that you have MinGW and Ninja installed.