gengeometry

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 Go to latest Published: Mar 17, 2024 License: Apache-2.0 Imports: 13 Imported by: 0

README

gengeometry

DO NOT USE!

This package will contain useful helper functions for working with polygons, lines, and all that.

Splitting a polygon / path

Simple algorithm for splitting a polygon along a line into different polygons.

alt text

Path and mesh generation

Really shitty path generation... this is mainly for experimenting with procedural generation of building shapes and all that. Not very good, but it works.

alt text

Documentation

Index

Constants

View Source 
const (
	RotateRight = iota
	RotateLeft
)

Variables

View Source 
var (
	BlockyOShape = BlockyShape{
		Width:  3,
		Length: 3,
		Set: []bool{
			true, true, true,
			true, false, true,
			true, true, true,
		},
	}

	BlockyUShape = BlockyShape{
		Width:  3,
		Length: 3,
		Set: []bool{
			true, false, true,
			true, false, true,
			true, true, true,
		},
	}

	BlockyLShape = BlockyShape{
		Width:  3,
		Length: 3,
		Set: []bool{
			true, false, false,
			true, false, false,
			true, true, true,
		},
	}

	BlockyJShape = BlockyShape{
		Width:  3,
		Length: 3,
		Set: []bool{
			false, true, true,
			false, false, true,
			true, true, true,
		},
	}

	BlockyTShape = BlockyShape{
		Width:  3,
		Length: 3,
		Set: []bool{
			true, true, true,
			false, true, false,
			false, true, false,
		},
	}

	BlockyPlusShape = BlockyShape{
		Width:  3,
		Length: 3,
		Set: []bool{
			false, true, false,
			true, true, true,
			false, true, false,
		},
	}
)
View Source 
var BlockyShapes = []BlockyShape{
	BlockyOShape,
	BlockyUShape,
	BlockyLShape,
	BlockyJShape,
	BlockyTShape,
	BlockyPlusShape,
}

Functions

func Abs 

func Abs(x float64) float64

func AngleOfSide 

func AngleOfSide(polygon []vectors.Vec2, i int) float64

AngleOfSide returns the absolute angle of the normal of the side of the polygon with the given index.

func CenterOfPath 

func CenterOfPath(points []vectors.Vec2) vectors.Vec2

CenterOfPath calculates the center of a polygon (by averaging all points).

func ContainsPoint 

func ContainsPoint(polygon []float64, pointX, pointY float64) bool

*

  • Checks, if polygon contains [x, y]. *
  • Works with simple polygons only. *
  • @param {number[]} polygon [x1, y1, x2, y2...]
  • @param {number} pointX Coordinate [x]
  • @param {number} pointY Coordinate [y]
  • @returns {boolean} depth

func DrawLine 

func DrawLine(img *image.RGBA, a, b vectors.Vec2, color color.RGBA, scale float64)

func GetBresenhamLine 

func GetBresenhamLine(pos1, pos2 vectors.IVec2) (points []vectors.IVec2)

GetBresenhamLine returns a list of points that are on the line between pos1 and pos2. The line is drawn using the Bresenham algorithm. See: http://www.roguebasin.com/index.php/Bresenham%27s_Line_Algorithm

func GetPathSides 

func GetPathSides(path []vectors.Vec2) []vectors.Segment

func InRectangle 

func InRectangle(a, b, c Point) bool

*

  • In Rectangle *
  • @private
  • @param {Point} a
  • @param {Point} b
  • @param {Point} c
  • @return {boolean}

func IsConvex 

func IsConvex(polygon []float64) bool

*

  • Checks, if polygon is convex. Polygon is convex, when each inner angle is <= 180°. *
  • @param {number[]} polygon [x1, y1, x2, y2...]
  • @returns {boolean}

func IsSimple 

func IsSimple(polygon []float64) bool

*

  • Checks, if polygon is simple. Polygon is simple, when its edges don't cross each other. *
  • @param {number[]} polygon [x1, y1, x2, y2...]
  • @returns {boolean} true if Polygon is simple

func PointInTriangle 

func PointInTriangle(px, py, ax, ay, bx, by, cx, cy float64) bool

*

  • Point in Triangle *
  • @private
  • @param {number} px
  • @param {number} py
  • @param {number} ax
  • @param {number} ay
  • @param {number} bx
  • @param {number} by
  • @param {number} cx
  • @param {number} cy
  • @returns {boolean}

func PolygonArrayToPolygon 

func PolygonArrayToPolygon(polygon []float64) []vectors.Vec2

*

  • [ v.x, v.y, v.x, v.y ]...

func PolygonToPolygonArray 

func PolygonToPolygonArray(polygon []vectors.Vec2) []float64

*

  • [ v.x, v.y, v.x, v.y ]...

func Reverse 

func Reverse(polygon []float64) []float64

*

  • Finds the point on polygon edges, which is closest to [x,y]. Returns an object in this format *
  • "dist" is the distance of the polygon point, "edge" is the number of the closest edge, "point" is the closest point on that edge, "norm" is the normal from "point" to [x,y]. *
  • @param {number[]} polygon [x1, y1, x2, y2...]
  • @param {number} x Coordinate [x]
  • @param {number} y Coordinate [y]
  • @returns {ClosestEdge}
  • @example
  • //={dist:0, edge:0, point:{x:0, y:0}, norm:{x:0, y:0}}
func ClosestEdge(polygon []float64, x, y float64) (isc ClosestEdge) {
	var p = polygon
	var l = len(p) - 2
	var empty = emptyPoints()
	var a1 = empty[0]
	var b1 = empty[2]
	var b2 = empty[3]
	// var c = tp[4] // is assigned a value but never used.
	a1.x = x
	a1.y = y

	isc.dist = math.Inf(1)

	for i := 0; i < l; i += 2 {
		b1.x = p[i]
		b1.y = p[i+1]
		b2.x = p[i+2]
		b2.y = p[i+3]
		isc = pointLineDist(a1, b1, b2, i>>1, isc)
	}
	b1.x = b2.x
	b1.y = b2.y
	b2.x = p[0]
	b2.y = p[1]
	isc = pointLineDist(a1, b1, b2, l>>1, isc)

	idst := 1 / isc.dist
	isc.norm.x = (x - isc.point.x) * idst
	isc.norm.y = (y - isc.point.y) * idst
	return isc
}

*

  • Reverse *
  • @param {number[]} polygon [x1, y1, x2, y2...]

func RotatePolygonAroundPoint 

func RotatePolygonAroundPoint(polygon []vectors.Vec2, point vectors.Vec2, angle float64) []vectors.Vec2

RotatePolygonAroundPoint rotates a polygon around a point by the given angle.

func SavePathAsPNG 

func SavePathAsPNG(path []vectors.Vec2, filename string, scale float64) error

SavePathAsPNG saves the path as a PNG image.

func ShrinkPath 

func ShrinkPath(points []vectors.Vec2, shrink float64) []vectors.Vec2

ShrinkPath shrinks a polygon by a given factor around its center.

func SimplifyPolyline 

func SimplifyPolyline(points []vectors.Vec2, tolerance float64, highestQuality bool) []vectors.Vec2

SimplifyPolyline simplifies a polyline. NOTE: This code is based on: https://github.com/mourner/simplify-js

func Slice 

func Slice(polygon []vectors.Vec2, startX, startY, endX, endY float64) ([][]vectors.Vec2, bool)

func StraightSkeleton 

func StraightSkeleton(points []vectors.Vec2, shrink, spacing float64) []vectors.Vec2

StraightSkeleton calculates the straight skeleton of a polygon. The straight skeleton is a graph of edges that can be used to generate a roof. See: https://github.com/feldhaus/coding-2d-cookbook/blob/main/js/geometry/polygon-straight-skeleton.js NOTE: This is a very naive implementation that only works for simple polygons. There are some issues wit NaN values and the added epsilon values make it not precise.

func TranslatePath 

func TranslatePath(path []vectors.Vec2, offset vectors.Vec2) []vectors.Vec2

TranslatePath translates a path by the given offset.

func Triangulate 

func Triangulate(polygon []vectors.Vec2) ([]int, error)

Triangulate triangulates a polygon using the ear clipping algorithm. It returns the indices of each vertex of each triangle in pairs of 3.

func TriangulatePolyk 

func TriangulatePolyk(polygon []float64) []int

*

  • Computes the triangulation. Output array is array of triangles (triangle = 3 indices of polygon vertices). *
  • Works with simple polygons only. *
  • @param {number[]} polygon [x1, y1, x2, y2...]
  • @returns {number[]} array of triangles (triangle = 3 indices of polygon vertices)
  • @example
  • var ids = PolyK.Triangulate([0, 0, 1, 0, 1, 1, 0, 1]);
  • //=[0, 1, 2, 0, 2, 3]

Types

type AABB 

type AABB struct {
	// contains filtered or unexported fields
}

func GetAABB 

func GetAABB(polygon []float64) AABB

*

  • Returns the Axis-aligned Bounding Box of polygon *
  • @param {number[]} polygon [x1, y1, x2, y2...]
  • @returns {AABB}
  • @example
  • //={x:0, y:0, width:0, height:0}

type BlockyShape 

type BlockyShape struct {
	Width, Length int    // Width and length of the shape in tiles
	Set           []bool // Set of tiles that are set
}

BlockyShape represents a shape that is made up of blocks / tiles.

func NewBlockyShape 

func NewBlockyShape(width, length int) BlockyShape

NewBlockyShape creates a new BlockyShape with the given width and length.

func NewRandShape 

func NewRandShape(width, length int) BlockyShape

func (BlockyShape) ConnectionPoints 

func (g BlockyShape) ConnectionPoints() []int

ConnectionPoints returns the indices of all tiles that are connection points. A connection point is a tile that has only one neighbor.

func (BlockyShape) GetConnectionDirection 

func (g BlockyShape) GetConnectionDirection(idx int) int

GetConnectionDirection returns the direction of the connection of the given index.

func (*BlockyShape) GetIsNeighborset 

func (g *BlockyShape) GetIsNeighborset(idx int) [4]bool

GetIsNeighborset returns a boolean array that indicates if the tile at the given index has a neighbor in the given direction.

The directions are: 0: Top 1: Bottom 2: Left 3: Right

func (BlockyShape) GetNeighbors 

func (g BlockyShape) GetNeighbors(idx int) []int

GetNeighbors returns the indices of all set neighbors of the given index.

func (BlockyShape) GetPaths 

func (g BlockyShape) GetPaths() [][]vectors.Vec2

GetPaths returns all closed paths that make up the shape. TODO: This is a very naive implementation that just adds each square as a path. It should be improved to merge squares that are next to each other.

func (BlockyShape) GetRotated 

func (g BlockyShape) GetRotated(rotateLeft bool, steps int) BlockyShape

func (BlockyShape) Print 

func (g BlockyShape) Print()

Print prints the shape to the console

func (BlockyShape) RenderToImage 

func (g BlockyShape) RenderToImage(img *image.RGBA, color color.RGBA)

RenderToImage renders the shape to a supplied image with the given color.

type CircleShape 

type CircleShape struct {
	Radius float64 // Radius of the circle
	Steps  int     // Number of points to use to draw the circle
}

CircleShape is a shape that is a circle.

func (CircleShape) ConnectionPoints 

func (c CircleShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the circle

func (CircleShape) GetPath 

func (c CircleShape) GetPath() []vectors.Vec2

GetPath returns the path of the circle

type Edge 

type Edge struct {
	Index int
	A     *Point
	B     *Point
}

type HShape 

type HShape struct {
	Width, Length float64
	WingWidth     float64
}

HShape is a shape that looks like an H.

func (HShape) ConnectionPoints 

func (h HShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the shape.

func (HShape) GetPath 

func (h HShape) GetPath() []vectors.Vec2

GetPath returns the path of the shape.

type ISC 

type ISC struct {
	Edge  *Edge
	Point *Point
	// contains filtered or unexported fields
}

type JShape 

type JShape struct {
	Width, Length, WingWidth float64
}

JShape is a shape that looks like a J.

func (JShape) ConnectionPoints 

func (j JShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the shape.

func (JShape) GetPath 

func (j JShape) GetPath() []vectors.Vec2

GetPath returns the path of the shape.

type LShape 

type LShape struct {
	Width, Length, WingWidth float64
}

LShape is a shape that looks like an L.

func (LShape) ConnectionPoints 

func (l LShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the shape.

func (LShape) GetPath 

func (l LShape) GetPath() []vectors.Vec2

GetPath returns the path of the shape.

type Mesh 

type Mesh struct {
	Vertices  []vectors.Vec3 // Contains the vertices of the mesh.
	Triangles []int          // Contains the indices of the triangle vertices.
}

Mesh represents a 3d mesh that can be exported to a .obj file.

func ExtrudePath 

func ExtrudePath(path []vectors.Vec2, height float64) (*Mesh, error)

ExtrudePath extrudes a path to a 3D shape.

func TaperPath 

func TaperPath(path []vectors.Vec2, height float64) (*Mesh, error)

TaperPath tapers a path to a 3D shape to generate a roof. NOTE: This is WIP since it doesn't get the angle right.

func (*Mesh) AddMesh 

func (m *Mesh) AddMesh(mesh *Mesh, position vectors.Vec3)

AddMesh adds a mesh to the current mesh (at a given vertical offset).

func (*Mesh) ExportToObj 

func (m *Mesh) ExportToObj(filename string)

ExportToObj exports the mesh to a .obj file.

func (*Mesh) Translate 

func (m *Mesh) Translate(v vectors.Vec2)

Translate translates the mesh by a given vector in the 2d plane.

type PlusShape 

type PlusShape struct {
	Width, Length, WingWidth float64
}

PlusShape is a plus shape.

func (PlusShape) ConnectionPoints 

func (p PlusShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the shape.

func (PlusShape) GetPath 

func (p PlusShape) GetPath() []vectors.Vec2

GetPath returns the path of the shape.

type Point 

type Point struct {
	// contains filtered or unexported fields
}

func GetLineIntersection 

func GetLineIntersection(a1, a2, b1, b2, c Point) (Point, bool)

Get Line Intersection

@private @param {Point} a1 @param {Point} a2 @param {Point} b1 @param {Point} b2 @param {Point} c @returns {Point}

type Polygon 

type Polygon struct {
	Points []vectors.Vec2
}

Polygon is a polygon with multiple points.

func (Polygon) DrawToImage 

func (p Polygon) DrawToImage(img *image.RGBA, color color.RGBA, scale float64)

DrawToImage draws the polygon to an image.

func (*Polygon) Split 

func (p *Polygon) Split(l vectors.Segment) []*Polygon

Split splits a polygon into multiple polygons by cutting it along a line. NOTE: This is buggy, especially when an intersection point is on a vertex.

type RectangleShape 

type RectangleShape struct {
	Width, Length float64
}

RectangleShape is a shape that is a rectangle.

func (RectangleShape) ConnectionPoints 

func (r RectangleShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the shape.

func (RectangleShape) GetPath 

func (r RectangleShape) GetPath() []vectors.Vec2

GetPath returns the path of the shape.

type Shape 

type Shape interface {
	ConnectionPoints() []vectors.Vec2 // Returns the connection points of the shape.
	GetPath() []vectors.Vec2          // Returns the path of the shape.
}

Shape is an interface for shapes.

type SquircleShape 

type SquircleShape struct {
	Width, Length, Radius float64
	Steps                 int
}

SquircleShape is a shape that is a squircle.

func (SquircleShape) ConnectionPoints 

func (s SquircleShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the squircle

func (SquircleShape) GetPath 

func (s SquircleShape) GetPath() []vectors.Vec2

GetPath returns the path of the squircle For a squircle, we just need to draw quarter circles at each corner, which will give us a squricle.

type TrapezoidShape 

type TrapezoidShape struct {
	Width, Length, WidthTop float64
}

TrapezoidShape is a shape that is a trapezoid.

func (TrapezoidShape) ConnectionPoints 

func (t TrapezoidShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the trapezoid

func (TrapezoidShape) GetPath 

func (t TrapezoidShape) GetPath() []vectors.Vec2

GetPath returns the path of the trapezoid

type TriangleShape 

type TriangleShape struct {
	Width, Length float64
}

TriangleShape is a shape that is a triangle.

func (TriangleShape) ConnectionPoints 

func (t TriangleShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the triangle

func (TriangleShape) GetPath 

func (t TriangleShape) GetPath() []vectors.Vec2

GetPath returns the path of the triangle

type UShape 

type UShape struct {
	Width, Length, WingWidth float64
}

UShape is a shape that looks like a U.

func (UShape) ConnectionPoints 

func (u UShape) ConnectionPoints() []vectors.Vec2

ConnectionPoints returns the connection points of the shape.

func (UShape) GetPath 

func (u UShape) GetPath() []vectors.Vec2

GetPath returns the path of the shape.

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