Bundles RBush and SAT.js for easy 2D collisions
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README.md

Crash

v2.0.2

Crash performs optimized 2D collisions, powered by RBush and SAT.js, written in javascript.
It's most obvious use-case is in game engines, but it's flexible enough to be used anywhere.
Crash is perfectly happy in the browser and on Node.js.

Contents

Installation

Just download one of the following files from this repo.

  1. crash.js: full source, with comments and all (14.2kB).
  2. crash.min.js: minified, ready to be used in production (6.1kB or 1.9kB gzipped).

Or get the code from NPM by typing the following command in a terminal (without the $):

$ npm install crash-colliders

You can find instruction on how to load Crash in your project below.
When you have installed Crash, head over to the Getting Started section.

Node.js or Browserify

Add the following snippet to your code:

var Crash = require("crash-colliders");

Now, you can use the API on the Crash variable.

Require.js

If you're using require.js in your project, use the following snippet to load Crash:

define(["path/to/crash"], function(Crash) {
    // Your code...
});

Now, you can use the API on the Crash variable in your module.

Browser Global

Add the following snippet to your HTML file:

<script type="text/javascript" src="path/to/crash.js"></script>

Now, you can use the API on the global Crash variable (window.Crash).

Getting Started

Before you can do anything useful with Crash, you have to create an instance. You can do this easily by calling:

var crash = new Crash();

new Crash() accepts one argument, an options object. This initializes some options (obviously), but discussing them would lead us too far and it's optional, so just leave it out for now to use the defaults. Check the API for more info.

Fun Fact: In version 1.x, Crash was just an object, ready to go. As a result, you couldn't create instances of it and you were stuck with 1 Crash object for your whole application. Starting from version 2.0.0, Crash is a constructor that creates objects that work (almost) exactly as the Crash object from 1.x. This means that you will almost always work on a Crash instance and never on the Crash constructor. The constructor does expose some methods, but those are also available on the prototype.

Important Fun Fact: Every Crash instance has its own Collider classes. This is necessary to make the Collider.insert(), Collider.remove(), Collider.update(), etc. work.

Adding Colliders

Now that everything is ready to roll, let's add some colliders. All colliders in Crash inherit from the crash.Collider class, which provides some basic methods that perform household tasks, like moving, updating its AABB and testing collisions. That would lead us too far, though, so I refer to the full API docs for more info.
All that stuff is awesome, but a Collider on its own isn't very useful: it doesn't have a shape. Before you can use a Collider, you have to give it a shape, but, luckily, Crash has some built-in ones for us. Let's try them out!

var point =   new crash.Point  (new crash.Vector(0,0));
var circle =  new crash.Circle (new crash.Vector(5,2),  10);
var box =     new crash.Box    (new crash.Vector(-40,0), 10, 15);
var polygon = new crash.Polygon(new crash.Vector(3,7),  [new crash.Vector(0,0), new crash.Vector(5,0), new crash.Vector(2,3)]);

Wow, what's all that!? Let's clarify this step by step.

  1. Each shape has its own constructor, e.g. a point is initialized with crash.Point etc.
  2. The first argument to each constructor is a Vector, setting the base position for the Collider. So, for a Point, this would be its position, for a Circle it would be the center and for a Box it would be the bottom-left corner.
  3. Some constructors take a few extra arguments:
  • Circle: the radius
  • Box: the width and height
  • Polygon: an array of Vectors, representing its corners, relative to the base position
  1. All the above arguments are required.
  2. These constructors also take two more (optional) arguments:
  • insert: a boolean indicating whether the collider should be inserted into RBush. More info on this is following in the next few steps.
  • data: some data to add to the collider. You can store anything you want here, but it doesn't do anything for Crash; it's just there for your convenience.

Fun Fact: the unit you use for the numbers is completely up to you. Crash only stores the numbers, you can interpret them as you wish, so you can use pixels, millimeters or even some game-specific unit you invented!

Another Fun Fact: it doesn't matter how you define position (e.g. top or bottom left corner for a Box etc.), as long as you use it consistently.

Important Fun Fact: there is a very important difference between Point and Vector: a Point is a Collider, so it can be used for collision checks. A Vector, on the other hand, is just an Object with x and y properties, used to define positions in Colliders, like the center of a Circle or the corners of a Polygon.

Testing for collisions

Now that we have some colliders, we would probably like to know if they are colliding. To do this, we use the crash.test() method:

if(crash.test(circle, box)) {
    alert("Oh my, we crashed!");
}

This is already quite nice, but not very useful: now we know that our colliders are touching, but we don't know how to undo this crash! Enter Response, the all-knowing crash guru.
First, let's create one:

var res = new crash.Response();

The Response class is copied from SAT, so for further information about the kind of info it provides, I refer to the SAT.js docs.

Then, let's do a subtle change to our testing code:

if(crash.test(circle, box, res)) {
    alert("Oh my, we crashed!");
}

Now, we can query the Response for some useful information and undo this embarassing crash:

if(crash.test(circle, box, res)) {
    alert("Oh my, we crashed!");
    var overlap = res.overlapV;
    circle.moveBy(-overlap.x, -overlap.y);
}

And just like that, our colliders aren't touching anymore!

Fun Fact: you could also use circle.test(box, res). This uses crash.test() under the hood, but it's a little more concise.

Unleashing the power of Crash

Wasn't that exciting!? Just wait for what's to come!
I assume you don't want to plow through heaps of loops and complex code to do everything we did in the previous steps for every frame and every collider.
That's where Crash's real power comes in. Let's insert() our colliders and get to some serious collision checking!

crash.insert(point);
crash.insert(circle);
crash.insert(box);
crash.insert(polygon);

You could have achieved the same by passing true for the insert argument of the constructors, like I mentioned at the beginning.

Fun Fact: just like you can use Collider.test() instead of crash.test(), you can use Collider.insert(), as a convenience method.

Now that our colliders have been inserted, we can let Crash do all the hard work: it will do all the collision checks for us! And because Crash leverages the power of RBush, only the checks that make sense will actually be performed, which saves a lot of resources.

Before we can let Crash do anything, we would like to make sure it can report to us what it's doing, so we can react to collisions. To do that, we add a listener with crash.onCollision(). This listener will be called every time a collision occurs.

var listener = function(a, b, res, cancel) {
    alert("Oh my, we crashed!");
}
crash.onCollision(listener);

Here, a and b are the colliders that are colliding, res is the all-knowing Response, and cancel is a function that cancels all further collision checks for this collider. This may be useful if you move the collider (rendering all the subsequent checks useless, as we will have to run them again for the new position) and/or when you use crash.check(), which we will cover in the next step.

Fun Fact: you can easily remove a listener with crash.offCollision(listener). Just make sure you saved it somewhere when you added it, so you can pass it to offCollision() as an argument!

And now, we're ready for some serious stuff:

crash.testAll(circle);

This runs collision checks for all inserted colliders that may be colliding with our circle. As our circle is colliding with all the other colliders, except our box, the listener we added previously will be called once for point and once for polygon, but not for box. For every call, a equals circle, b the respective collider and res gives us some info about the collision.

Fun Fact: Note that, like with crash.test(), we can pass in a Response, but we don't have to. If we don't, Crash will make one for us and pass that around to the listeners. How convenient!

What kind of sorcery is this !?

We can even go one step further: let's make Crash do everything!

For this to work, we need to make sure that we call crash.moved() on all the colliders that have moved:

Fun Fact: you probably already guessed: you can use Collider.moved() instead!

crash.moved(point);
crash.moved(circle);

This way, Crash will know it only has to call testAll for these colliders, the ones that have moved.

And, now, ladies and gentleman, the holy grail of collision checking:

crash.check();

And it's done. All checks have run, our colliders are where they should be. With just one function call. Such wow.

But what's up with that moved()?

All the built-in methods (like moveTo, setOffset and rotate) already call this for you, so you don't have to worry about this. You should only worry when you insert a collider for the first time. Normally, when designing your game (or anything else), you would make sure your colliders aren't already colliding when you load them. When this is the case, though, you can call crash.checkAll() just after you loaded your colliders. This will do the same as check(), but for all colliders, not just the ones that moved. Neat, isn't it?

Contributing

All contributions are very welcome!
Typos, bug fixes, code cleanup, documentation, tests, a website, you name it!

Questions and feature requests belong in the issue tracker, with the right tags.

Overview

Or: about the check() loop

In this section, I'll explain the basics of Crash, how it works, how the methods fit together and what the basic workflow is.

In this section, I'll assume you're using Crash to power a game (engine), because that's probably what the majority will be using it for, and not having to cover all the edge cases makes it easier to explain.

The very heart of Crash is its crash.check() loop: this is where all the magic is happening. During the update cycle of your game (engine), you can move your objects around freely (probably using some physics) and not care about collisions; just move them to where you would like them to be. You can move the Colliders either by using the move functions (moveBy, rotate,...), which is the easiest way, or by setting their x and y coordinates. If you're using the latter, you have to be cautious.
After every move, a few things have to happen:

  1. The AABB of the Collider must be updated. Use crash.updateAABB() to achieve this.
  2. The Collider's position in RBush must be updated. Use crash.update() for this, but be aware that this calls also crash.updateAABB()! You could also manually remove() and re-insert() the collider in rbush, just like update() is doing.
  3. The Collider must be added to crash.__moved in order for it to be collision checked during the next crash.check(). Use crash.addToMoved() to achieve this. You could also add it manually, but make sure you're no adding it twice (that would be a waste of resources).

1. and 2. can be bundled in one crash.update() call, and all the above can be bundled in one crash.moved() call, which is the method the move functions are calling for you. This is why using the move functions is the easiest: all this is done for you.

When all your Colliders are in place, just call crash.check(). This will iterate over crash.__moved and do the following for every Collider (this happens in crash.testAll()). Let's call this loop A.

First, all the possible collisions are retrieved using RBush, with a crash.search(). Then, for every possibly colliding collider (loop B), Crash will test for a collision using SAT, and if there is, it will call crash.__onCollision(), which in turn calls the Listeners, passing in the two Colliders and the Response of the collision. If, during this crash.__onCollision(), crash.BREAK is set to true, loop B is stopped. This can happen when, for example, the first collider (that will be the one passed from A to B) is moved inside a Listener; the Collider will then be added to crash.__moved and thus be checked in the next iteration of loop A, making everything that happens in B useless (it will be done again in the next iteration of A, and the possible collisions may not be accurate anymore). This doesn't happen when the second Collider passed to Listeners (the one 'generated' by B) is moved, because it will just be added to crash.__moved to be handled in the next iteration of A, but doesn't render everything happening inside B useless (it's the first Collider that is our focus).
At the end of loop B (so, for every iteration of A), the Collider passed from A to B has its lastPos set to a copy of its position at that moment.
Then, crash.testAll() (loop B) returns, and the next iteration of A begins.

At the end of crash.check() (loop A), all the Colliders that have been processed have their lastCheckedPos set to a copy of their position at that time.

I hope this has helped to clarify some of Crash's misty bits. If it hasn't, let me know and/or take a look at the source: it's not that complex and it's not that much.

API

Crash

This is the main object, returned by require(), injected by defined() or set as window.Crash. Anything related to Crash sits in this namespace.
Create a new instance of Crash like this:

var crash = new Crash(options);

Where options is an object as defined below.

__options : object

Private
The (normalized) options passed to the constructor. Three (optional) properties are being used by Crash:

maxEntries : number (9)

This option is passed to RBush, so I refer to the RBush docs for more info on this.
Default: 9

maxChecks : number (100)

The maximum amount of times to run crash.testAll() during crash.check(). See crash.check() for more info.
This sets crash.MAX_CHECKS.
Default: 100

overlapLimit : number|false (0.5)

The minimum amount two crash.Colliders should overlap to call the Listeners. If falsy, overlapLimit will not be taken into account. See crash.testAll() for more info.
This sets crash.OVERLAP_LIMIT.
Default: 0.5

crash.RBush : function

The RBush constructor, as returned by the rbush module.

crash.SAT : object

The SAT object, as returned by the SAT.js module.

crash.Vector : constructor

Alias: crash.V
Represents a vector, used by the Colliders to define their positions and corners, and by SAT to perform its calculations.
I refer to the SAT docs for the API definition.

crash.V : constructor

Alias: crash.Vector
Alias for crash.Vector.

crash.Response : constructor

Provides information about a collision, like overlap distance and direction.
I refer to the SAT docs for the API definition.

crash.rbush : RBush

The RBush instance that holds the colliders. This is (mostly) used internally to optimize collision checks.
For further documentation, please see the RBush docs.

crash.RESPONSE : Response

Used by the testing functions. When no Response has been passed to them, they use this instead.

crash.BREAK : boolean

Whether to stop the currently running check loop. This is set to true by crash.cancel(). See crash.testAll() for more info.

crash.MAX_CHECKS : number

The maximum amount of times to run crash.testAll() during crash.check(). See crash.check() for more info.

crash.OVERLAP_LIMIT : number

The minimum amount two crash.Colliders should overlap to call the Listeners. If falsy, OVERLAP_LIMIT will not be taken into account. See crash.testAll() for more info.

crash.__listeners : Array.<function>

Private
An array of functions to call when a collision occurs. You can add to this with crash.onCollision().

crash.__moved : Array.<Collider>

Private
An array of colliders that have moved since the last crash.check(). This is used internally by crash.check() to optimize collision checks. For more info, see crash.check().

crash.insert (Collider collider) - .

collider: Collider. The crash.Collider to insert.
return: Crash. For chaining.

Inserts crash.Colliders in crash.rbush. Before crash.Colliders turn up in crash.search()s or in collision checks (performed by crash.testAll()), you must crash.insert() them.
You can use crash.remove() to get them out.

var circle = new crash.Circle(new crash.V(0,0), 5);
// circle won't turn up in searches and collision checks
crash.insert(circle);
// Now it will!

crash.remove (Collider collider) - .

collider: Collider. The crash.Collider to remove.
return: Crash. For chaining.

Removes crash.Colliders from crash.rbush.

crash.insert(collider);
// collider will turn up in searches and collision checks
crash.remove(collider);
// now, it won't, anymore

crash.all () - Collider[]

return: Array.<Collider>. An array containing all the crash.Colliders that have been crash.insert()ed.

Returns all the crash.Colliders that have been crash.insert()ed.

var allColliders = crash.all();

crash.search (Collider collider) - Collider[]

collider: Collider. The crash.Collider to base the search on.
return: Array.<Collider>. An array of colliders that may be colliding with collider.

Runs rbush.search() based on a crash.Collider, which will look for all crash.Colliders that have (nearly) colliding axis-aligned bounding boxes (AABBs). This search is optimized by an RTree (that's a special algorithm, designed for this), implemented by RBush.

RBush usually requires an array of AABB coordinates to perform a search, so crash.search() translates the crash.collider's aabb coordinates to the correct array.

The array returned by rbush.search() may contain one or more references of collider (that's the one passed into the method). crash.search() filters out these referenc

var possibleCollisions = crash.search(collider);
// returns an array containing closeByCollider, but not veryFarAwayCollider

crash.clear() - .

return: Crash. For chaining.

Clears crash from all crash.Colliders. This calls rbush.clear(), and clears crash.__moved.

crash.addToMoved (Collider collider) - .

collider: Collider. The crash.Collider that should be added to crash.__moved.
return: Crash. For chaining.

Adds a crash.Collider to crash.__moved, so it gets collision checked during the next crash.check() round. This does not update the Collider's AABB! If you want to do both, use crash.moved() instead.
Note that the built-in move methods of Colliders (moveBy, rotate,...) already call crash.moved() (which calls addToMoved()) for you.

collider.pos.x += 5;
// Is not taken into account in the next check() round

crash.moved(collider);
// Now it will
collider.moveBy(5,0);
// crash.moved(collider), and thus crash.addToMoved(collider), has already been called for you

crash.update (Collider collider) - .

collider: Collider. The crash.Collider that should be updated.
return: Crash. For chaining.

Updates the aabb of the crash.Collider (using crash.updateAABB()) and updates its position in RBush.

crash.moved (Collider collider) - .

collider: Collider. The crash.Collider that has moved.
return: Crash. For chaining.

Notifies crash that a crash.Collider has moved. This calls crash.update() and crash.addToMoved(), so all the housekeeping is done in one function call. Note that this is already taken care of for you when using the built-in move methods of the Colliders (moveBy, rotate,...).

collider.pos.x += 5;
// Is not taken into account in the next check() round
// and the aabb is not updated

crash.moved(collider);
// Now it will
// and its aabb is updated
collider.moveBy(5,0);
// crash.move(collider) has already been called for you

crash.reset () - .

return: Crash. For chaining.

Resets crash with the options passed to the constructor. This basically calls crash.clear() and resets some variables.
This method is primarily used by the test suite.

crash.cancel () - false

return: false. Makes it easy to stop event propagation in some EventEmitters.

This method cancels the current check loop. When you call crash.check(), a loop will start, which calls crash.testAll() for every collider that has moved since the last crash.check(). Then, crash.testAll() will do a crash.search() and perform all the necessary checks, calling crash.__onCollision() for every collision. Now, if you move a collider during the crash.testAll() loop (i.e. in a Listener), it will be added to crash.__moved and all the following collision checks become unnecessary, because they will run again in the next iteration of the crash.check() loop.
That's where crash.cancel() comes in. When you move a collider inside a Listener, call crash.cancel() (or the fourth argument of the listener, which is the exact same function) to cancel all further (unnecessary) collision checks.

crash.onCollision(function(a, b, res, cancel) {
    a.moveBy(-res.overlapV.x, -res.overlapV.y);
    cancel();
});

Important Note: all the above is only valid for the first collider (named a), because that's the one that collision checks are run for. If yo move b, nothing has to be done.

crash.onCollision(function(a, b, res, cancel) {
    b.moveBy(res.overlapV.x, res.overlapV.y);
});

crash.getTestString (string type1, string type2) - string

type1: string. The type of the first crash.Collider.
type2: string. The type of the second crash.Collider.
return: string. The appropriate SAT testing string.

Gives you the right SAT method name to test for a collision between two crash.Colliders. Be sure to pass Collider.type, ans not a crash.Collider!

var circle = new crash.Circle(new crash.Vector(0,0), 10);
var box = new crash.Box(new crash.Vector(5,5), 7, 15);

var string = crash.getTestString(circle.type, box.type); // 'testCirclePolygon'

crash.onCollision (function listener) - .

listener: function. The Listener to add to the collision event. See Listener for more info.
return: Crash. For chaining.

Adds a Listener to crash.__listeners and will be called every time a collision occurs. See Listener for more info.

var listener = function(a, b, res, cancel) {
    alert("Oh my, there is a collision!");
    a.moveBy(-res.overlapV.x, -res.overlapV.y);
}
crash.onCollision(listener);

crash.offCollision (function listener) - .

listener: function. The Listener to remove. return: Crash. For chaining.

Removes a Listener from the collision event. So, this is the opposite of crash.onCollision().

crash.offCollision(listener);

crash.__onCollision (Collider a, Collider b, Response res) - .

Private
a: Collider. The crash.Collider that collides with b.
b: Collider. The crash.Collider that collides with a.
res: Response. The crash.Response for thsi collision.
return: Crash. For chaining.

Calls all the Listeners when a collision event occurs. It takes three arguments: the two crash.Colliders that are colliding and the crash.Response for this collision. It will take care of injecting crash.cancel() by itself.
Intended for private use.

crash.extend (function child, function base) - undefined

child: function. This constructor that inherits from parent.
base: function. The constructor that is the parent of child.
return: undefined.

Extends the prototype chain of base to child, so child inherits from base. This is used to make the collider classes inherit from Collider.

var Child = function(){}
var Parent = function(){}
crash.extend(Child, Parent);

crash.updateAABB (Collider collider) - .

collider: Collider. The crash.Collider whose AABB should be updated.
return: Crash. For chaining.

Calls crash.updateAABBPolygon(), crash.updateAABBBox(), crash.updateAABBCircle() or crash.updateAABBPoint() based on collider's type.

crash.updateAABBPolygon (Polygon collider) - .

collider: Polygon. The crash.Polygon whose AABB should be updated.
return: Crash. For chaining.

Updates a crash.Polygon's aabb attribute (Collider.aabb), based on its position and size.

crash.updateAABBBox (Box collider) - .

collider: Box. The crash.Box whose AABB should be updated.
return: Crash. For chaining.

Updates a crash.Box's aabb attribute (Collider.aabb), based on its position and size.

crash.updateAABBCircle (Circle collider) - .

collider: Circle. The crash.Circle whose AABB should be updated.
return: Crash. For chaining.

Updates a crash.Circle's aabb attribute (Collider.aabb), based on its position and size.

crash.updateAABBPoint (Point collider) - .

collider: Point. The crash.Point whose AABB should be updated.
return: Crash. For chaining.

Updates a crash.Point's aabb attribute (Collider.aabb), based on its position.

crash.test (Collider a, Collider b, [Response res]) - boolean

a: Collider. The first crash.Collider to test for.
b: Collider. The second crash.Collider to test for.
res: Response|optional. The optional crash.Response to use.
return: boolean. Indicates whether there is a collision between aand b.

Tests for a collision between a and b, using SAT. The boolean return value indicates whether a and b are colliding: true if there is a collision, false otherwise.
You can optionally pass in a crash.Response to get some information about the collision (if there is one). If you don't, crash.RESPONSE will be used instead.

var c1 = new crash.Circle(new crash.V(0,0), 5);
var c2 = new crash.Point(new crash.V(3,0));
var c3 = new crash.Box(new crash.V(15,20), 10, 10);
var res = new crash.Response();

crash.test(c1, c2, res);
// true, info in 'res'

crash.test(c1, c3);
//false, info in crash.RESPONSE

crash.testAll (Collider collider, [Response res]) - boolean

collider: Collider. The crash.Collider to test collisions for.
res: Response|optional. The optional crash.Response to use.
return: boolean. Whether the loop was stopped.

Tests for collisions between collider and any crash.Collider that has been crash.insert()ed in crash.rbush. This will crash.search() for collider, do a collision check for every crash.Collider returned by that search and finally call crash.__onCollision() for every collision.
You can stop this loop (the one that checks for collisions) simply by calling crash.cancel(). This sets crash.BREAK to true (which is what testAll actually looks for). In Listeners, the recommended way is to call their cancel argument, which is the exact same function as crash.cancel().
Stopping the loop comes in handy when you move collider in any of the Listeners, because all consequent collision checks become unnecessary: you will have to run testAll() again for the new position.
The value returned by testAll() indicates whether the loop was cancelled: if it was, false is returned, otherwise, it returns true.

You probably don't want to use this method, because it isn't really intended to be used publicly (but rather by crash.check() internally), and crash.check() is more convenient in most situations anyway.

Finally, I would like to note a few things:

  1. res is optional: if you don't pass it, crash.RESPONSE will be used instead.
  2. this method doesn't really provide direct feedback, like crash.test() does: it rather calls the attached Listeners. This means res (or crash.RESPONSE) will be passed to the Listeners, and will only hold info about the last collision when the call is finished.
  3. if this method returns false, the loop was cancelled, so you probably want to run it again.
  4. testAll will not run [crash.__onCollision()] when the overlap is smaller than [crash.OVERLAP_LIMIT]. If [crash.OVERLAP_LIMIT] is falsy, [crash.__onCollision] will always be called.
  5. testAll won't call crash.update() on collider, so make sure it's updated.
  6. testAll is not really intended to be used publicly, but rather by crash.check() internally.
var c1 = new crash.Circle(new crash.V(0,0), 5, true);
var c2 = new crash.Point(new crash.V(3,0), true);
var c3 = new crash.Box(new crash.V(15,20), 10, 10, true);
var res = new crash.Response();
crash.onCollision(function(a, b, res, cancel){
    alert("Oh my, there is a collision!");
});

crash.testAll(c1, res);
// calls the listener for (c1, c2), but not for (c1, c3).
// the response passed to the listener is 'res'.

crash.test(c2);
// calls the listener for (c2, c1), but not for (c2, c3).
// the response passed to the listener is crash.RESPONSE.

crash.test(c3);
// the listener will not be called.

crash.check () - .

return: Crash. For chaining.

Calls crash.testAll() for every crash.Collider in crash.__moved. This means that it performs collision checks for all the crash.Colliders that have moved since the last crash.check(), which makes it the perfect function to handle collisions after everything was moved to new positions by physics. This integrates neatly in game loops: just do your updates, and then call crash.check() to handle collisions.

Important to note is that Colliders may be moved inside Listeners: they will be added to crash.__moved and checked in further iterations of the (current) crash.check() loop.
To prevent infinite loops (a collider is moved, checked in the following iteration, moved again, etc.), the loop will be forced to stop after crash.MAX_CHECKS loops, which is 100 by default.

For a crash.Collider to be checked, crash must be notified it has moved (i.e. it must be pushed to crash.__moved. You can use crash.moved() or crash.addToMoved() to achieve this.

// apply updates to colliders ...
// things may be colliding!
crash.check();
// nothing is colliding anymore!
// if the right listeners have been added, that is.

crash.checkAll () - .

return: Crash. For chaining.

This does the same as crash.check(), with one difference: it doesn't check crash.Colliders in crash.__moved, but rather all crash.Colliders (as returned by crash.all()). This is especially handy when you just loaded you crash.Colliders and you don't know which ones are colliding and/or have moved.

// I have no idea what's up with my Colliders:
// I haven't moved any yet, but I don't know if any are colliding!
crash.checkAll();
// Ahh, that's better! Everything is sorted out!

crash.Collider (string type, SAT.Polygon|SAT.Circle satCollider, [boolean insert:false], [any data]) : constructor

type: string. The type of collider this is. Valid values: polygon, box, point, circle.
satCollider: SAT.Polygon or SAT.Circle. The SAT Collider to use for collision checks.
insert: boolean|optional. Whether to crash.insert() this Collider.
data: any|optional. Some data to store in Collider.data.
return: Collider. The new Collider.

This is the main Collider constructor, which provides some housekeeping methods, like moveBy, update, etc. All the other constructors (crash.Polygon, crash.Box, crash.Point and crash.Circle) inherit from this class. They pass their type and a custom SAT Collider to crash.Collider, and pass through insert and data. This way, they inherit the housekeeping functions from Collider's prototype and they can add their own on their own prototype.

Collider.type : string

The type of collider this is. Valid values: polygon, box, point, circle.
This attribute is used by crash.updateAABB() to determine how to update the Collider.aabb attribute.

Collider.sat : SAT.Polygon|SAT.Circle

The actual SAT collider used to do the collision checking. For crash.Polygons, crash.Boxes and crash.Points, this is a SAT.Polygon, for crash.Circles, this is a SAT.Circle.
For further documentation, I refer to the SAT.js docs.

Collider.data : any

Some data that has to be carried around with the crash.Collider. It can be of any type, and doesn't mean anything to Crash; it's just for your convenience.

Collider.pos : Vector

This is the same crash.Vector as Collider.sat.pos (so collider.pos === collider.sat.pos is true).
This position is not garanteed to be 'safe', i.e. the crash.Collider may still be colliding with something. Collider.pos is the crash.Vector that is moved by Collider.moveTo() and Collider.moveBy(), and is therefore always the most up-to-date, but not always collision checked.

Collider.lastPos : Vector

This is a crash.Vector keeping track of the last position as it was at the end of the crash.testAll() loop. So, during a crash.check() loop, the Collider.lastPos attribute as it is inside the Listeners, is a copy of Collider.pos at the end of the previous iteration.

Collider.lastCheckedPos : Vector

This is a crash.Vector keeping track of the last fully collision checked position of the crash.Collider, i.e. a copy of Collider.pos at the end of the crash.check() loop.

Collider.aabb : object

An Object with x1, y1, x2 and y2 attributes, that keeps track of the crash.Collider's axis-aligned bounding box (AABB). It is used to perform crash.search()es.
When you move a crash.Collider, don't forget to update this attribute, with crash.updateAABB(). Note that the built-in move methods (moveBy, rotate, etc.) already do this for you.

Collider.insert () - .

return: Collider. For chaining.

Shortcut for crash.insert().

Collider.remove () - .

return: Collider. For chaining.

Shortcut for crash.remove().

Collider.update () - .

return: Collider. For chaining.

Shortcut for crash.update().

Collider.updateAABB () - .

return: Collider. For chaining.

Shortcut for crash.updateAABB().

Collider.moved () - .

return: Collider. For chaining.

Shortcut for crash.moved().

Collider.search () - Collider[]

return: Array.<Collider>. An array of crash.Colliders that may be colliding with this.

Shortcut for crash.search().

Collider.setData (any data) - .

data: any. The data to set as the new Collider.data.
return: Collider. For chaining.

Sets the data attribute (Collider.data) to any value that's passed as the first argument. See Collider.data for more info.

Collider.getData () - any

return: any. The value of the data attribute (Collider.data).

Returns the value of the data attribute (Collider.data). See Collider.data for more info.

Collider.moveTo (number x, number y) - .

x: number. The x-coordinate to move to.
y: number. The y-coordinate to move to.
return: Collider. For chaining.

This moves the crash.Collider's pos (Collider.pos) and sat.pos attributes to (x, y). This calls Collider.moved() for you.

Collider.moveBy (number x, number y) - .

Alias: Collider.move()
x: number. The distance in x direction to move by.
y: number. The distance in y direction to move by.
return: Collider. For chaining.

This moves the crash.Collider's pos (Collider.pos) and sat.pos attributes by (x, y). This calls Collider.moved() for you.

Collider.move (number x, number y) - .

Alias: Collider.moveBy()
x: number. The distance in x direction to move by.
y: number. The distance in y direction to move by.
return: Collider. For chaining.

Alias of Collider.moveBy().

crash.Polygon (Vector pos, Vector[] points, [boolean insert:false], [any data]) ~ crash.Collider

Inherits from: crash.Collider
pos: Vector. The base position of the Polygon.
points: Array.<Vector>. The points/corners of the Polygon.
insert: boolean|optional. Whether to insert the Polygon.
data: any|optional. Any data to set as Collider.data.
return: Polygon.

A Polygon is a crash.Collider with a base position (Collider.pos) and a few points/corners. The points are defined by an array of crash.Vectors, relative to the base position (Collider.pos), in counter-clockwise order.
For the insert and data arguments, see crash.Collider.

Polygon.setPoints (Vector[] points) - .

points: Array.<Vector>. The points/corners of the Polygon.
return: Polygon. For chaining.

A shortcut for Collider.sat.setPoints(), which calls Collider.moved() for you.

Polygon.setAngle (number angle) - .

angle: number. The angle by which to rotate the Polygon (in radians).
return: Polygon. For chaining.

A shortcut for Collider.sat.setAngle(), which calls Collider.moved() for you.

Polygon.setOffset (number offset) - .

offset: number. The offset by which to translate the points of the Polygon.
return: Polygon. For chaining.

A shortcut for Collider.sat.setOffset(), which calls Collider.moved() for you.

Polygon.rotate (number angle) - .

angle: number. The angle by which to rotate the points of the Polygon.
return: Polygon. For chaining.

A shortcut for Collider.sat.rotate(), which calls Collider.moved() for you.

crash.Circle (Vector center, number radius, [boolean insert:false], [any data]) ~ crash.Collider

center: Vector. The position of the center of the Circle.
radius: number. The radius of the Circle.
insert: boolean|optional. Whether to insert the Circle.
data: any|optional. Any data to set as Collider.data. return: Circle

A Circle is a crash.Collider, with a center and radius.
For the insert and data arguments, see crash.Collider.

crash.Point (Vector position, [boolean insert:false], [any data]) ~ crash.Collider

position: Vector. The position of the Point.
insert: boolean|optional. Whether to insert the Point.
data: any|optional. Any data to set as Collider.data. return: Point

A Point is a crash.Collider with just a position. It doesn't have a size.
For the insert and data arguments, see crash.Collider.

crash.Box (Vector position, number width, number height, [boolean insert:false], [any data]) ~ crash.Collider

position: Vector. The position of the Box.
width: number. The width of the Box.
height: number. The height of the Box.
insert: boolean|optional. Whether to insert the Box.
data: any|optional. Any data to set as Collider.data. return: Box

A Box is a crash.Collider in a rectangular shape with a position (the bottom-left corner), a width and a height.
For the insert and data arguments, see crash.Collider.

Listener (Collider a, Collider b, Response res, function cancel) : function

a: Collider. The crash.Collider that collides with b.
b: Collider. The crash.Collider that collides with a.
res: Response. The crash.Response for this collision.
cancel: function. Cancels the current check loop. See crash.testAll() for more info.

A listener is a function that is called every time a collision is detected by crash.testAll(), crash.check() or crash.checkAll() and will be passed four arguments: the two crash.Colliders that are colliding, the crash.Response for this collision and crash.cancel(), which cancels the current check loop. See crash.testAll() for more info about this.
The context of the listener (this) will be set to crash.
You can add a listener with crash.onCollision() and you can remove them with crash.offCollision(). All listeners are stored in crash.__listeners, which is intended for private use.

License

The MIT License (MIT)

Copyright (c) 2014-2017 Tuur Dutoit

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.