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Committed At | 2018-09-20 01:41:19 UTC |

`elm-geometry`

is an Elm package for working with 2D and
3D geometry. It provides a wide variety of geometric data types such as points,
vectors, arcs, spline curves and coordinate frames, along with functions for
transforming and combining them in many different ways. You can:

- Rotate points around axes in 3D
- Mirror triangles across 3D planes
- Project 3D geometry into 2D sketch planes
- Measure distances and angles between different objects
- Convert objects between different coordinate systems
- Compose complex 2D/3D transformations
- ...and much more!

A wide variety of data types are supported:

`Point2d`

,`Point3d`

,`Vector2d`

,`Vector3d`

,`Direction2d`

,`Direction3d`

`Axis2d`

,`Axis3d`

,`Plane3d`

`Frame2d`

,`Frame3d`

,`SketchPlane3d`

`BoundingBox2d`

,`BoundingBox3d`

`LineSegment2d`

,`LineSegment3d`

,`Triangle2d`

,`Triangle3d`

`Polyline2d`

,`Polyline3d`

,`Polygon2d`

`Circle2d`

,`Circle3d`

,`Arc2d`

,`Arc3d`

`Ellipse2d`

,`EllipticalArc2d`

`QuadraticSpline2d`

,`QuadraticSpline3d`

,`CubicSpline2d`

,`CubicSpline3d`

A large range of geometric functionality is included, such as various forms of constructors...

```
Point3d.fromCoordinates ( 1, 4, 5 )
Direction2d.fromAngle (degrees 30)
Point3d.midpoint p1 p2
Vector2d.withLength 3 Direction2d.y
Triangle2d.fromVertices ( p1, p2, p3 )
-- fit a plane through three points
Plane3d.throughPoints p1 p2 p3
Axis3d.through Point3d.origin Direction3d.z
Arc2d.from p1 p2 (degrees 90)
QuadraticSpline3d.with
{ startPoint = p1
, controlPoint = p2
, endPoint = p3
}
CubicSpline2d.fromEndpoints
{ startPoint = p1
, startDerivative = v1
, endPoint = p2
, endDerivative = v2
}
```

...point/vector arithmetic...

```
Vector3d.sum v1 v2
-- the vector from the point p1 to the point p2
Vector2d.from p1 p2
Vector3d.crossProduct v1 v2
Vector2d.length vector
-- distance of a point from the origin point (0, 0)
point |> Point2d.distanceFrom Point2d.origin
```

...2D/3D transformations...

```
Vector2d.rotateBy (degrees 45) vector
Point2d.rotateAround Point2d.origin (degrees 45) point
Point3d.mirrorAcross Plane3d.xy point
Vector3d.projectionIn Direction3d.z vector
Triangle3d.rotateAround Axis3d.x (degrees 45) triangle
lineSegment
|> LineSegment3d.mirrorAcross Plane3d.yz
|> LineSegment3d.projectOnto Plane3d.xy
Plane3d.offsetBy 3 Plane3d.xy
```

...and conversions between coordinate systems:

```
rotatedFrame =
Frame2d.atOrigin |> Frame2d.rotateBy (degrees 30)
-- convert from global coordinates to local coordinates
-- (relative to the given coordinate frame)
Vector2d.relativeTo rotatedFrame vector
-- convert from local coordinates (relative to the given
-- coordinate frame) to global coordinates
Point2d.placeIn rotatedFrame point
-- convert from global 3D coordinates to local 2D
-- coordinates in the given sketch plane
point2d =
Point3d.projectInto SketchPlane3d.yz point3d
-- convert from local 2D coordinates in the given
-- sketch plane back to global 3D coordinates
point3d =
Point3d.on SketchPlane3d.yz point2d
```

Assuming you have installed Elm and
started a new project, you can install `elm-geometry`

by running

```
elm install ianmackenzie/elm-geometry
```

in a command prompt inside your project directory.

Full API documentation
is available for each module. Most modules are associated with a particular data
type (for example, the `Point3d`

module contains functions for creating and manipulating `Point3d`

values).

Following the Elm package design guidelines,
most `elm-geometry`

modules are designed to be imported exposing only the
corresponding types, and using the module name as a prefix for everything else:

```
import Point3d exposing (Point3d)
import Axis3d exposing (Axis3d)
rotatedPoint : Point3d
rotatedPoint =
Point3d.rotateAround Axis3d.x (degrees 30) originalPoint
```

Please open a new issue
if you run into a bug, if any documentation is missing/incorrect/confusing, or
if there's a new feature that you would find useful. For general questions about
using `elm-geometry`

, the best place is probably the **#geometry** channel on
the friendly Elm Slack:

You can also try:

- Sending me (
**@ianmackenzie**) a message on Slack - even if you don't have any particular questions right now, it would be great to know what you're hoping to do with the package! - Posting to the Elm Discourse forums
- Or if you happen to be in the New York area, come on out to the Elm NYC meetup =)

You can also find me on Twitter (@ianemackenzie),
where I occasionally post `elm-geometry`

-related stuff like demos or new
releases. Have fun, and don't be afraid to ask for help!