geometry2d

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layout: default title: Geometry 2D

2D Geometry

Overview

2D geometric primitives including circles, axis-aligned bounding boxes, capsules, edges, planes, polygons, and triangles. Also includes raycasting and collision manifold types for 2D collision detection.

Why Use This?

These primitives are the building blocks for 2D physics engines, collision detection, spatial queries, and computational geometry.

Shapes

Circle

A circle defined by center point and radius.

Types: lm2_circle_f64, lm2_circle_f32, lm2_circle (default = f32)

Structure:

typedef struct lm2_circle_f32 {
    lm2_v2_f32 center;
    float radius;
} lm2_circle_f32;

Functions:

Function	Description
lm2_circle_make_f32(center, radius)	Create from center and radius
lm2_circle_make_coords_f32(x, y, radius)	Create from coordinates
lm2_circle_unit_f32()	Unit circle at origin
lm2_circle_area_f32(c)	Area
lm2_circle_circumference_f32(c)	Circumference
lm2_circle_diameter_f32(c)	Diameter
lm2_circle_contains_point_f32(c, point)	Point-in-circle test (returns bool)
lm2_circles_overlap_f32(a, b)	Circle-circle overlap (returns bool)
lm2_circle_contains_circle_f32(a, b)	Circle containment (returns bool)
lm2_circle_translate_f32(c, offset)	Translate circle
lm2_circle_scale_f32(c, scale)	Scale radius

AABB2

2D axis-aligned bounding box. See lm2_aabb2.h.

Capsule2

A 2D capsule (rounded rectangle) defined by two endpoints and a radius. See lm2_capsule2.h.

Edge2

A 2D line segment defined by two endpoints. See lm2_edge2.h.

Plane2

A 2D plane (line) defined by normal and distance. See lm2_plane2.h.

Polygon

A 2D convex polygon. See lm2_polygon.h.

Triangle2

A 2D triangle with construction and property functions. See lm2_triangle2.h.

Additional triangle geometry functions (area, barycentric coordinates, circumcenter, incircle, etc.) in lm2_triangle2_geometry.h.

Shape2

A generic 2D shape container that can represent any of the above primitives. See lm2_shape2.h.

Raycasting

lm2_raycast2.h provides ray-shape intersection queries for 2D shapes.

Collision Manifolds

lm2_manifold2.h provides contact information for 2D collision pairs, including contact points, normals, and penetration depths.

Example

lm2_circle_f32 c = lm2_circle_make_coords_f32(0, 0, 5.0f);
lm2_v2_f32 point = lm2_v2_make_f32(3.0f, 4.0f);

bool inside = lm2_circle_contains_point_f32(c, point);  // true (dist=5, radius=5)
float area = lm2_circle_area_f32(c);                     // ~78.54