pico_hit.h File Reference

Separating Axis Theorem (SAT) Tests written in C99. More...

#include "pico_math.h"

Include dependency graph for pico_hit.h:

Go to the source code of this file.

Classes
struct	ph_circle_t
	A circle shape. More...
struct	ph_poly_t
	A polygon shape Must use CCW (counter-clockwise) winding. More...
struct	ph_ray_t
	A ray (directed line segment) More...
struct	ph_manifold_t
	A collision manifold Provides information about a collision. Normals always point from shape 1 to shape 2. More...
struct	ph_raycast_t
	Raycast information. More...

Macros
#define	PICO_HIT_MAX_POLY_VERTS   16

Functions
ph_circle_t	ph_make_circle (pv2 pos, pfloat radius)
	Initializes a circle.
ph_poly_t	ph_make_poly (const pv2 vertices[], int vertex_count)
	Initializes a polygon.
ph_ray_t	ph_make_ray (pv2 pos, pv2 dir, pfloat dist)
	Constructs a ray.
ph_poly_t	ph_aabb_to_poly (const pb2 *aabb)
	Converts and axis-aligned bounding box (AABB) to a polygon.
bool	ph_sat_poly_poly (const ph_poly_t *poly_a, const ph_poly_t *poly_b, ph_manifold_t *manifold)
	Tests to see if one polygon overlaps with another.
bool	ph_sat_poly_circle (const ph_poly_t *poly, const ph_circle_t *circle, ph_manifold_t *manifold)
	Tests to see if a polygon overlaps a circle.
bool	ph_sat_circle_poly (const ph_circle_t *circle, const ph_poly_t *poly, ph_manifold_t *manifold)
	Tests to see if a circle overlaps a polygon.
bool	ph_sat_circle_circle (const ph_circle_t *circle_a, const ph_circle_t *circle_b, ph_manifold_t *manifold)
	Tests to see if two circles overlap.
bool	ph_ray_line (const ph_ray_t *ray, pv2 s1, pv2 s2, ph_raycast_t *raycast)
	Tests if ray intersects a (directed) line segment.
bool	ph_ray_poly (const ph_ray_t *ray, const ph_poly_t *poly, ph_raycast_t *raycast)
	Tests if ray intersects a polygon.
bool	ph_ray_circle (const ph_ray_t *ray, const ph_circle_t *circle, ph_raycast_t *raycast)
	Tests if ray intersects a circle.
pv2	ph_ray_at (const ph_ray_t *ray, pfloat dist)
	Finds the point along the ray at the specified distance from the origin.
ph_poly_t	ph_transform_poly (const pt2 *transform, const ph_poly_t *poly)
	Transforms a polygon using an affine transform.
ph_circle_t	ph_transform_circle (const pt2 *transform, const ph_circle_t *circle)
	Transforms a circle using an affine transform.
pb2	ph_poly_to_aabb (const ph_poly_t *poly)
	Returns the bounding box for the given polygon.
pb2	ph_circle_to_aabb (const ph_circle_t *circle)
	Returns the bounding box for the given circle.

Detailed Description

Separating Axis Theorem (SAT) Tests written in C99.

---

Licensing information at end of header

Features:

• Written in C99
• Single header library for easy build system integration
• Tests overlaps for AABBs, polygons, and circles using SAT
• Provides collision information including the normal and amount of overlap
• Ray casts against line segments, polygons, and circles
• Permissive license (MIT)

Summary:

The Separating Axis Theorem (SAT) roughly states that two convex shapes do not intersect if there is an axis separating them. In the case of simple shapes the theorem provides necessary and sufficient conditions. For example, in the case of convex polygons, it is sufficient to test the axises along the edge normals of both polygons.

SAT tests are reasonably efficient and are frequently used for static, narrow phase, collision detection in games.

This library provides SAT tests for polygons, AABBs (which are, of course, polygons), and circles. Manifold objects can be passed to test functions so that, in the case of a collision, they will contain the colliding edge normal, overlap (minimum translational distance or MTD), and a vector (minimum translation vector or MTV).

Rays (directed line segments) can be cast against line segments, polygons, and circles. Aside from reporting hits, the normal at and distance to the point of impact is also available.

IMPORTANT: Polygons in this library use counter-clockwise (CCW) winding. See the ph_aabb_to_poly for an example.

Usage:

To use this library in your project, add the following

‍#define PICO_HIT_IMPLEMENTATION #include "pico_hit.h"

to a source file (once), then simply include the header normally.

Dependencies:

This library depends on "pico_math.h", which must be in the include path. You must also add

‍#define PICO_MATH_IMPLEMENTATION #include "pico_math.h"

to the same or other source file (once).

Macro Definition Documentation

PICO_HIT_MAX_POLY_VERTS

#define PICO_HIT_MAX_POLY_VERTS   16

Function Documentation

ph_make_circle()

ph_circle_t ph_make_circle	(	pv2	pos,
		pfloat	radius
	)

Initializes a circle.

Parameters

pos	Circle center
radius	Circle radius

ph_make_poly()

ph_poly_t ph_make_poly	(	const pv2	vertices[],
		int	vertex_count
	)

Initializes a polygon.

Parameters

vertex_count	The number of vertices of the polygon
vertices	The vertices of the polygon (must use CCW winding)

Returns

The polygon with the given vertices

ph_make_ray()

ph_ray_t ph_make_ray	(	pv2	pos,
		pv2	dir,
		pfloat	dist
	)

Constructs a ray.

Parameters

pos	The origin of the array
dir	The direction of the ray
dist	The length of the ray

ph_aabb_to_poly()

ph_poly_t ph_aabb_to_poly

(

const pb2 *

aabb

)

Converts and axis-aligned bounding box (AABB) to a polygon.

aabb The AABB

Returns

the AABB as a polygon

ph_sat_poly_poly()

bool ph_sat_poly_poly	(	const ph_poly_t *	poly_a,
		const ph_poly_t *	poly_b,
		ph_manifold_t *	manifold
	)

Tests to see if one polygon overlaps with another.

Parameters

poly_a	The colliding polygon
poly_b	The target polygon
manifold	The collision manifold to populate (or NULL)

Returns

True if the polygons overlap and false otherwise

ph_sat_poly_circle()

bool ph_sat_poly_circle	(	const ph_poly_t *	poly,
		const ph_circle_t *	circle,
		ph_manifold_t *	manifold
	)

Tests to see if a polygon overlaps a circle.

Parameters

poly	The colliding polygon
circle	The target circle
manifold	The collision manifold to populate (or NULL)

Returns

True if the polygon and circle overlap, and false otherwise

ph_sat_circle_poly()

bool ph_sat_circle_poly	(	const ph_circle_t *	circle,
		const ph_poly_t *	poly,
		ph_manifold_t *	manifold
	)

Tests to see if a circle overlaps a polygon.

Parameters

circle	The colliding circle
poly	The target polygon
manifold	The collision manifold to populate (or NULL)

Returns

True if the circle overlaps the polygon, and false otherwise

ph_sat_circle_circle()

bool ph_sat_circle_circle	(	const ph_circle_t *	circle_a,
		const ph_circle_t *	circle_b,
		ph_manifold_t *	manifold
	)

Tests to see if two circles overlap.

Parameters

circle_a	The colliding circle
circle_b	The target circle
manifold	The collision manifold to populate (or NULL)

Returns

True if the circle and the other circle, and false otherwise

ph_ray_line()

bool ph_ray_line	(	const ph_ray_t *	ray,
		pv2	s1,
		pv2	s2,
		ph_raycast_t *	raycast
	)

Tests if ray intersects a (directed) line segment.

Parameters

ray	Ray to test
s1	First endpoint of segment
s2	Second endpoint of segment
raycast	Normal and distance of impact (or NULL)

Returns

True if the ray collides with the line segment and false otherwise

ph_ray_poly()

bool ph_ray_poly	(	const ph_ray_t *	ray,
		const ph_poly_t *	poly,
		ph_raycast_t *	raycast
	)

Tests if ray intersects a polygon.

Parameters

ray	Ray to test
poly	The polygon
raycast	Normal and distance of impact (or NULL). May terminate early if NULL

Returns

True if the ray collides with the polygon and false otherwise

ph_ray_circle()

bool ph_ray_circle	(	const ph_ray_t *	ray,
		const ph_circle_t *	circle,
		ph_raycast_t *	raycast
	)

Tests if ray intersects a circle.

Parameters

ray	Ray to test
circle	The circle
raycast	Normal and distance of impact (if not NULL).

Returns

True if the ray collides with the circle and false otherwise

ph_ray_at()

pv2 ph_ray_at	(	const ph_ray_t *	ray,
		pfloat	dist
	)

Finds the point along the ray at the specified distance from the origin.

ph_transform_poly()

ph_poly_t ph_transform_poly	(	const pt2 *	transform,
		const ph_poly_t *	poly
	)

Transforms a polygon using an affine transform.

Parameters

transform	The transform
poly	The polygon to transform

Returns

A new polygon

ph_transform_circle()

ph_circle_t ph_transform_circle	(	const pt2 *	transform,
		const ph_circle_t *	circle
	)

Transforms a circle using an affine transform.

Parameters

transform	The transform
poly	The circle to transform

Returns

A new circle

ph_poly_to_aabb()

pb2 ph_poly_to_aabb

(

const ph_poly_t *

poly

)

Returns the bounding box for the given polygon.

ph_circle_to_aabb()

pb2 ph_circle_to_aabb

(

const ph_circle_t *

circle

)

Returns the bounding box for the given circle.