collidex

defmodule Collidex do
  @moduledoc """
  ## Usage

  ### Points

  Cartesian points are 2-tuples of the form {x, y}. I picked this format for
  speed and for compatibility with [certrel/graphmath](https://hex.pm/packages/graphmath).

  ### Geometric primitives

  Circles, Rects (grid-aligned rectangles), and Polygons are Elixir structs.
  Each module has a make() function for creating them in common formats.

  #### Circles
  Circles can be made from three arguments (center_x, center_y, radius), or a
  3-tuple specifying the same values.

  ```
  iex> Collidex.Geometry.Circle.make(0.0, 0.0, 1.0)
  %Collidex.Geometry.Circle{center: {0.0, 0.0}, radius: 1.0}

  iex> Collidex.Geometry.Circle.make(1.0, 1.0, 1.0)
  %Collidex.Geometry.Circle{center: {1.0, 1.0}, radius: 1.0}
  ```

  #### Rects

  Rects are grid-aligned rectangles delineated by two opposite corners.
  `Rect.make` takes a pair of vectors:

  ```
  iex(1)> Collidex.Geometry.Rect.make({0.0, 0.0}, {1.0, 1.0})
  %Collidex.Geometry.Rect{a: {0.0, 0.0}, b: {1.0, 1.0}}
  ```

  For convenience, you may omit the braces and just specify four numbers:
  ```
  iex(2)> Collidex.Geometry.Rect.make(0.0, 0.0, 1.0, 1.0)
  %Collidex.Geometry.Rect{a: {0.0, 0.0}, b: {1.0, 1.0}}
  ```

  #### Polygons

  Specify polygons as an array of vectors:

  ```
  iex(3)> Collidex.Geometry.Polygon.make([{0.0, 0.0}, {1.0, 1.0}, {2.0, 0.0}, {1.0, -1.0}])
  %Collidex.Geometry.Polygon{vertices: [{0.0, 0.0}, {1.0, 1.0}, {2.0, 0.0},
    {1.0, -1.0}]}
  ```

  ### Detecting Collisions Between primitives

  Pass any pair of primitives to Collidex.Detector.collision?/3. A truthy return
  value indicates that they overlap on the plane. The third argument is an
  optional atom representing the detection method for Polygon-to-Polygon collisions
  and defaults to :accurate. For faster but less accurate comparisons, specify :fast.

  ### Detecting collisions between and within lists of primitives

  ... coming soon

  """
end