Geometry

Generic immutable 2D geometry library for game development.

Uses a top-left origin with +Y down. This only affects directional getters (Top, Bottom, Up, Down).

Installation

go get github.com/gravitton/geometry

Usage

import geom "github.com/gravitton/geometry"

p1 := geom.Pt(1, 2)
p2 := geom.Pt(3, 4)

v := p2.Subtract(p1) // Vector
if v.Equal(geom.Vec(2, 2)) { ... }

r := geom.Rect(p1, geom.Sz(10, 5))
if r.Contains(p2) { ... }

hex := geom.Hexagon(p1, geom.SzU(20), geom.FlatTop)
for _, vertex := range hex.Vertices() { ... }

Matrix transforms:

m := geom.IdentityMatrix().Rotate(math.Pi / 4).Scale(2, 2)
p := geom.Pt(1.0, 0.0).Transform(m)

Type aliases for common numeric types (ints, floats):

import (
    "github.com/gravitton/geometry/types/floats"
    "github.com/gravitton/geometry/types/ints"
)

type Grid struct {
    Size     ints.Size
    CellSize floats.Size
}

API

All types are generic over the Number constraint:

type Number interface {
    ~int | ~int8 | ~int16 | ~int32 | ~int64 | ~float32 | ~float64
}

Full documentation is available at pkg.go.dev/github.com/gravitton/geometry.

Types

Type	Constructor	Description
Point[T]	Pt(x, y)	2D position
Vector[T]	Vec(x, y)	2D displacement
Size[T]	Sz(w, h), SzU(n)	Width and height
Rectangle[T]	Rect(center, size), RectFromMin, RectFromMinMax, RectFromSize	Axis-aligned rectangle (center + size)
Circle[T]	Circ(center, r)	Circle (center + radius)
Line[T]	Ln(start, end)	Line segment
Polygon[T]	Pol(vertices)	Arbitrary polygon
RegularPolygon[T]	RegPol(center, size, n, angle), Triangle, Square, Hexagon	Regular polygon
Padding[T]	Pad(t,r,b,l), PadU(n), PadXY(tb, lr)	Top/Right/Bottom/Left padding
Matrix	Mat(a,b,c,d,e,f), IdentityMatrix(), TranslationMatrix, RotationMatrix, ScaleMatrix	2D affine matrix (float64)

Conventions

All methods return new values — no mutation.

Every type exposes .Int(), .Float(), and implements String(), Equal(), IsZero().

Types with spatial extent also implement Bounds() Rectangle[T].

Collision

CollisionRectangles[T](a, b Rectangle[T]) bool
CollisionCircles[T](a, b Circle[T]) bool
CollisionRectangleCircle[T](r Rectangle[T], c Circle[T]) bool

Image interop

PointFromImage[T](p image.Point) Point[T]
SizeFromImage[T](r image.Rectangle) Size[T]
RectFromImage[T](r image.Rectangle) Rectangle[T]

(Point[T]).Point() image.Point
(Rectangle[T]).Rectangle() image.Rectangle

Math utilities

Lerp[T](a, b T, t float64) T
Clamp[T](v, min, max T) T
Equal[T](a, b T) bool          // within Delta (1e-6)
EqualDelta[T](a, b T, d float64) bool
Midpoint[T](a, b T) T
Abs[T](a T) T
Multiply[T](a T, factor float64) T
Divide[T](a T, factor float64) T
ToRadians(deg float64) float64
ToDegrees(rad float64) float64

Credits

• Tomáš Novotný
• All Contributors

License

The MIT License (MIT). Please see License File for more information.