vec-la

    1.5.0 • Public • Published

    vec

    Tiny linear algebra library specifically for 2d.

    See it in action: https://codepen.io/fstokesman/pen/aWgEXv

    Installation

    npm install --save vec-la

    and import or require as needed. If you need to use a standalone windowed version in a script tag:

    <script src="node_modules/vec-la/dist/vec.window.js"></script>

    Features

    • Immutable functions for manipulating vectors
    • Vectors and matrices represented as pure, single dimensional arrays
    • Immutable Matrix builder helper object for sequentially composing matrices

    API

    • vec.add(v, v2) : Result of adding v and v2
    • vec.sub(v, v2) : Result of subtracting v2 from v
    • vec.scale(v, sc) : Result of multiplying components of v by sc
    • vec.midpoint(v, v2) : Midpoint between v and v2
    • vec.norm(v) : Result of normalising v
    • vec.mag(v) : Magnitude of v
    • vec.normal(v): Normal vector of v
    • vec.towards(v, v2, t): A point in the interval [v, v2] along the direction formed from v2 - v1. t is a normalalised percentage [0, 1] of where in the interval the point falls.
    • vec.rotate(v, a) : Result of rotating v around the origin by a radians
    • vec.rotatePointAround(v, cp, a) : Result of rotating v around cp by a radians
    • vec.dot(v, v2) : Dot product of v and v2
    • vec.det(v) : Determinant of v
    • vec.dist(v, v2) : Euclidean distance between v and v2
    • vec.matrixBuilder(m) : Creates a matrix builder (see below)
    • vec.createMatrix(a, b, c, d, tx, ty) : Helper function for matrix creation. Defaults to an identity matrix
    • vec.transform(v, m) : Result of applying matrix tranformation m to v
    • vec.composeTransform(m, m2) : Result of composing transformation matrix m with m2

    Finally, when using the window version you can call vec.polute() to insert these functions into the global scope with the naming convention:

    vFunctionName e.g vAdd, vMidpoint, vDot etc.

    Matrix Builder

    vec.matrixBuilder(m) creates a builder object that can be used to easily chain together transformations. Call get() on the builder at any time to get a copy of the matrix at that point.

    const mb = vec.matrixBuilder(); // Defaults to identity matrix
    const finalMatrix = mb
      .rotate(Math.PI/6)
      .scale(2, 3)
      .shear(0.2, 0)
      .translate(20, 40)
      .get();
     
    // [ 
    //  2.0320508075688775, -0.48038475772933664, 20,
    //  1.4999999999999998, 2.598076211353316, 40,
    //  0, 0, 1
    // ]

    The function also accepts a matrix as it's argument.

    • rotate(a) : Concatenate a rotation matrix of a radians
    • scale(x, y) : Concatenate a scaling matrix
    • shear(x, y) : Concatenate a shearing matrix
    • translate(x, y) : Concatenate a translation matrix
    • add(m) : Concatenate an arbitrary matrix
    • get() : Return the resulting matrix

    Tests

    Clone the repository, and then run npm install && npm test.

    Examples

    (all examples assume vec is imported under vec)

    Addition

    const v1 = [0, 1];
    const v2 = [1, 0];
    const v3 = vec.add(v1, v2); // [1, 1]

    Scaling

    const v1 = [0, 1];
    const scaler = 10;
    const v2 = vec.scale(v1, scaler); // [0, 10]

    Normalising

    const v1 = [6.32, -23.1];
    const v2 = vec.norm(v1); // [0.2638946146581466, -0.9645515187663272]

    Magnitude

    const v1 = [6.32, -23.1];
    const mag = vec.mag(v1); // 23.948954048141644

    Matrix Transform

    const v1 = [10, 10];
     
    // Inversion matrix
    const m = [
      -1, 0,  0
       0, -1, 0,
       0,  0, 1
    ];
    const v2 = vec.transform(v1, m); // [-10, -10]

    Computing determinants

    const m = [
      10, 0, 0,
      0, 10, 0,
      0,  0, 1
    ];
    const d = vec.det(m); // 100

    Composing Matrices

    const v = [10, 10];
    const m = [
      0, -1, 0,
      -1, 0, 0,
       0, 0, 1
    ];
    const m2 = [
      Math.cos(Math.PI/2), -Math.sin(Math.PI/2), 0,
      Math.sin(Math.PI/2), Math.cos(Math.PI/2)   0,
      0, 0, 1
    ];
    const m3 = vec.composeTransform(m2, m);
     
    const v2 = vec.transform(v1, m1); // is the same as
    const v3 = vec.transform(vec.transform(v1, m), m2);

    Motivation

    Many linear algebra libraries represent their vectors as object like { x, y, mutableMethod, ... }, which can be cumbersome to work with. Arrays are easier to map, reduce, combine and generally work with symbolically. Additionally, Vec is designed to be used with ES6 and thus the ... rest syntax, and so can easily and cleanly be supplied to functions expecting x and y parameters as sequential arguments.

    For example:

    ctx.arc(...point, radius, 0, 2 * Math.PI, false);

    Keywords

    none

    Install

    npm i vec-la

    DownloadsWeekly Downloads

    109

    Version

    1.5.0

    License

    MIT

    Last publish

    Collaborators

    • francisstokes