geometryFl.h File Reference

Detailed Description

Design Philosophy

These utility functions are can be used for geometric math with floating point numbers.

Much of this file was adapted from https://www.jeffreythompson.org/collision-detection/

Usage

No initialization or deinitialization is required. Each function will not modify the given shapes. See the functions below for what is provided and how to use them.

Example

circleFl_t circ = {
    .pos.x  = 2.5f,
    .pos.y  = 5.5f,
    .radius = 8.5f,
};
rectangleFl_t rect = {
    .pos.x  = -2.5f,
    .pos.y  = -4.5f,
    .width  = 6.5f,
    .height = 9.5f,
};
if (circleRectFlIntersection(circ, rect, NULL))
{
    printf("Shapes intersect\n");
}
else
{
    printf("Shapes do not intersect\n");
}

Go to the source code of this file.

Data Structures
struct	circleFl_t
	Signed integer representation of a circle. More...
struct	rectangleFl_t
	Signed integer representation of a rectangle. More...
struct	lineFl_t
	Signed integer representation of a line segment. More...

Macros
#define	EPSILON   0.0001f

Functions
bool	circleCircleFlIntersection (circleFl_t circle1, circleFl_t circle2, vecFl_t *collisionPoint, vecFl_t *collisionVec)
	Check if two circles intersect.
bool	circlePointFlIntersection (circleFl_t circle, vecFl_t point, vecFl_t *collisionVec)
	Check if a point and a circle intersect.
bool	circleRectFlIntersection (circleFl_t circle, rectangleFl_t rect, vecFl_t *collisionVec)
	Check if a circle and a rectangle intersect.
bool	circleLineFlIntersection (circleFl_t circle, lineFl_t line, bool checkEnds, vecFl_t *cpOnLine, vecFl_t *collisionVec)
	Check if a circle and a line intersect.
int16_t	circleInfLineFlIntersectionPoints (circleFl_t circle, lineFl_t line, vecFl_t *intersection_1, vecFl_t *intersection_2)
	Find the points of intersection between a circle's circumference and a line. There may be zero (no intersection), one (tangent), or two points of intersection.
bool	rectRectFlIntersection (rectangleFl_t rect1, rectangleFl_t rect2, vecFl_t *collisionVec)
	Check if two rectangles intersect.
bool	rectLineFlIntersection (rectangleFl_t rect, lineFl_t line, vecFl_t *collisionVec)
	Check if a line intersects with a rectangle.
bool	lineLineFlIntersection (lineFl_t a, lineFl_t b, vecFl_t *intersection)
	Check if two lines intersect.
vecFl_t	infLineIntersectionPoint (lineFl_t a, lineFl_t b)
	Find the intersection point between two infinitely long lines.
lineFl_t	getLineBoundingBox (lineFl_t line)
	Get a bounding box around a line where p1.x < p2.x and p1.y < p2.y.
int16_t	circleLineSegFlIntersection (circleFl_t circle, lineFl_t line, lineFl_t boundingBox, vecFl_t *intersections)
	Check if a line segment intersects with a circle. This uses circleInfLineFlIntersectionPoints().

---

Data Structure Documentation

circleFl_t

struct circleFl_t

Data Fields
vecFl_t	pos	The position of the center of the circle.
float	radius	The radius of the circle.

rectangleFl_t

struct rectangleFl_t

Data Fields
vecFl_t	pos	The position the top left corner of the rectangle.
float	width	The width of the rectangle.
float	height	The height of the rectangle.

lineFl_t

struct lineFl_t

Data Fields
vecFl_t	p1	One end point of the line segment.
vecFl_t	p2	The other end point of the line segment.

Macro Definition Documentation

EPSILON

#define EPSILON   0.0001f

A small value to account for floating point rounding errors

Function Documentation

circleCircleFlIntersection()

bool circleCircleFlIntersection	(	circleFl_t	circle1,
		circleFl_t	circle2,
		vecFl_t *	collisionPoint,
		vecFl_t *	collisionVec )

Check if two circles intersect.

Parameters

circle1	[IN] One circle to check for intersection, assumed to be moving
circle2	[IN] The other circle to check for intersection, assumed to be fixed
collisionPoint	[OUT] The point at which the two circles collide, on the circumference of circle2. May be NULL
collisionVec	[OUT] A vector pointing from the second circle to the first in the direction of the collision. May be NULL.

Returns

true if the circles intersect or touch, false if they do not

circlePointFlIntersection()

bool circlePointFlIntersection	(	circleFl_t	circle,
		vecFl_t	point,
		vecFl_t *	collisionVec )

Check if a point and a circle intersect.

Parameters

circle	[IN] A circle to check for intersection
point	[IN] A point to check for intersection
collisionVec	[OUT] A vector pointing from the point to the circle in the direction of the collision. May be NULL.

Returns

true if the point intersects or touches the circle, false if it doesn't

circleRectFlIntersection()

bool circleRectFlIntersection	(	circleFl_t	circle,
		rectangleFl_t	rect,
		vecFl_t *	collisionVec )

Check if a circle and a rectangle intersect.

Adapted from https://www.jeffreythompson.org/collision-detection/circle-rect.php

Parameters

circle	[IN] The circle to check for intersection
rect	[IN] The rectangle to check for intersection
collisionVec	[OUT] A vector pointing from the rectangle to the circle in the direction of the collision. May be NULL.

Returns

true if the shapes intersect or touch, false if they do not

circleLineFlIntersection()

bool circleLineFlIntersection	(	circleFl_t	circle,
		lineFl_t	line,
		bool	checkEnds,
		vecFl_t *	cpOnLine,
		vecFl_t *	collisionVec )

Check if a circle and a line intersect.

Adapted from https://www.jeffreythompson.org/collision-detection/line-circle.php

Parameters

circle	[IN] A circle to test intersection
line	[IN] A line to test intersection
checkEnds	[IN] True to check the points at the end of the line, false to ignore them
cpOnLine	[OUT] The closest point on the line to the circle
collisionVec	[OUT] A vector pointing from the line to the circle in the direction of the collision. This may be NULL.

Returns

true if the circle intersects the line, false if it doesn't

circleInfLineFlIntersectionPoints()

int16_t circleInfLineFlIntersectionPoints	(	circleFl_t	circle,
		lineFl_t	line,
		vecFl_t *	intersection_1,
		vecFl_t *	intersection_2 )

Find the points of intersection between a circle's circumference and a line. There may be zero (no intersection), one (tangent), or two points of intersection.

See https://cp-algorithms.com/geometry/circle-line-intersection.html

Parameters

circle	[IN] The circle to check for intersection
line	[IN] The line to check for intersection
intersection_1	[OUT] If it exists, the first intersection will be written to this pointer
intersection_2	[OUT] If it exists, the second intersection will be written to this pointer

Returns

The number of intersections, between 0 and 2. intersection_1 is filled before intersection_2.

rectRectFlIntersection()

bool rectRectFlIntersection	(	rectangleFl_t	rect1,
		rectangleFl_t	rect2,
		vecFl_t *	collisionVec )

Check if two rectangles intersect.

Adapted from https://www.jeffreythompson.org/collision-detection/rect-rect.php

Parameters

rect1	[IN] One rectangle to check for intersection
rect2	[IN] The other rectangle to check for intersection
collisionVec	[OUT] A vector pointing from the second rectangle to the first in the direction of the collision. May be NULL.

Returns

true if the rectangles intersect or touch, false if they do not

rectLineFlIntersection()

bool rectLineFlIntersection	(	rectangleFl_t	rect,
		lineFl_t	line,
		vecFl_t *	collisionVec )

Check if a line intersects with a rectangle.

Adapted from https://www.jeffreythompson.org/collision-detection/line-rect.php

Parameters

rect	[IN] A rectangle to check for intersection
line	[IN] A line to check for intersection
collisionVec	[OUT] A vector pointing from the rectangle to the line in the direction of the collision. May be NULL.

Returns

true if the line intersects the rectangle, false if it doesn't

lineLineFlIntersection()

bool lineLineFlIntersection	(	lineFl_t	a,
		lineFl_t	b,
		vecFl_t *	intersection )

Check if two lines intersect.

Adapted from https://www.jeffreythompson.org/collision-detection/line-line.php

Parameters

a	[IN] One line to check for intersection
b	[IN] Another line to check for intersection
intersection	[OUT] The point at which the two lines intersect. May be NULL

Returns

true if the lines intersect, false if they do not

infLineIntersectionPoint()

vecFl_t infLineIntersectionPoint	(	lineFl_t	a,
		lineFl_t	b )

Find the intersection point between two infinitely long lines.

Parameters

a	One infinitely long line
b	Another infinitely long line

Returns

The intersection, or (FLT_MAX, FLT_MAX) for parallel lines

getLineBoundingBox()

lineFl_t getLineBoundingBox

(

lineFl_t

line

)

Get a bounding box around a line where p1.x < p2.x and p1.y < p2.y.

Parameters

line	The line to get a bounding box for

Returns

The bounding box

circleLineSegFlIntersection()

int16_t circleLineSegFlIntersection	(	circleFl_t	circle,
		lineFl_t	line,
		lineFl_t	boundingBox,
		vecFl_t *	intersections )

Check if a line segment intersects with a circle. This uses circleInfLineFlIntersectionPoints().

Parameters

circle	[IN] The circle to check for intersection
line	[IN] The line to check for intersection
boundingBox	[IN] The bounding box of the line, found with getLineBoundingBox()
intersections	[OUT] Array of two vecFl_t. If it exists, the intersections will be written to this pointer

Returns

The number of intersections between this line segment and the circle