raycaster

Note: This documentation is for the old 0.8.0 version of A-Frame. Check out the documentation for the current 1.6.0 version

The raycaster component provides line-based intersection testing with a raycaster. Raycasting is the method of extending a line from an origin towards a direction, and checking whether that line intersects with other entites.

The raycaster component uses the three.js raycaster. The raycaster checks for intersections at a certain interval against a list of objects, and will emit events on the entity when it detects intersections or clearing of intersections (i.e., when the raycaster is no longer intersecting an entity).

The cursor component and laser-controls components both build on top of the raycaster component.

Example

<a-entity id="player" collider-check>
  <a-entity raycaster="objects: .collidable" position="0 -0.9 0" rotation="90 0 0"></a-entity>
</a-entity>
<a-entity class="collidable" geometry="primitive: box" position="1 0 0"></a-entity>

AFRAME.registerComponent('collider-check', {
  dependencies: ['raycaster'],

  init: function () {
    this.el.addEventListener('raycaster-intersected', function () {
      console.log('Player hit something!');
    });
  }
});

Properties

Property	Description	Default Value
autoRefresh	Whether to automatically refresh raycaster’s list of objects to test for intersection using mutation observers to detect added or removed entities and components.	true
direction	Vector3 coordinate of which direction the ray should point from relative to the entity’s origin.	0, 0, 0
enabled	Whether raycaster is actively checking for intersections.	true
far	Maximum distance under which resulting entities are returned. Cannot be lower then `near`.	Infinity
interval	Number of milliseconds to wait in between each intersection test. Lower number is better for faster updates. Higher number is better for performance.	0
near	Minimum distance over which resuilting entities are returned. Cannot be lower than 0.	0
objects	Query selector to pick which objects to test for intersection. If not specified, all entities will be tested.	null
origin	Vector3 coordinate of where the ray should originate from relative to the entity’s origin.	0, 0, 0
recursive	Checks all children of objects if set. Else only checks intersections with root objects.	true
showLine	Whether or not to display the raycaster visually with the line component.	false
useWorldCoordinates	Whether the raycaster origin and direction properties are specified in world coordinates.	false

Events

The raycaster component is useful because of the events it emits on entities. It will emit events on both the raycasting entity and the intersected entities.

Event Name	Description
raycaster-intersected	Emitted on the intersected entity. Entity is intersecting with a raycaster. Event detail will contain `el`, the raycasting entity, and `intersection`, an object containing detailed data about the intersection.
raycaster-intersected-cleared	Emitted on the intersected entity. Entity is no longer intersecting with a raycaster. Event detail will contain `el`, the raycasting entity.
raycaster-intersection	Emitted on the raycasting entity. Raycaster is intersecting with one or more entities. Event detail will contain `els`, an array with the intersected entities, and `intersections`, an array of objects containing detailed data about the intersections.
raycaster-intersection-cleared	Emitted on the raycasting entity. Raycaster is no longer intersecting with one or more entities. Event detail will contain `clearedEls`, an array with the formerly intersected entities.

Intersection Object

The event detail contains intersection objects. They are returned straight from three.js Raycaster.intersectObjects.:

Property	Description
distance	distance between the origin of the ray and the intersection
point	point of intersection, in world coordinates
face	intersected face
faceIndex	index of the intersected face
indices	indices of vertices comprising the intersected face
object	the intersected object
uv	U,V coordinates at point of intersection

Members

Member	Description
intersectedEls	Entities currently intersecting the raycaster.
objects	three.js objects to test for intersections. Will be `scene.children` if not `objects` property is not specified.
raycaster	three.js raycaster object.

Methods

Method	Description
refreshObjects	Refreshes the list of objects based off of the `objects` property to test for intersection.

Whitelisting Entities to Test for Intersection

We usually don’t want to test everything in the scene for intersections (e.g., for collisions or for clicks). Selective intersections are good for performance to limit the number of entities to test for intersection since intersection testing is an operation that will run over 60 times per second.

To select or pick the entities we want to test for intersection, we can use the objects property. If this property is not defined, then the raycaster will test every object in the scene for intersection. objects takes a query selector value:

<a-entity raycaster="objects: .clickable" cursor></a-entity>
<a-entity class="clickable" geometry="primitive: box" position="1 0 0"></a-entity>
<a-entity class="not-clickable" geometry="primitive: sphere" position="-1 0 0"></a-entity>

Manually Refreshing the Target Entities of the Raycaster

The raycaster component keeps a local array of objects and entities that the raycaster tests against for intersection. This array defaults to every 3D object in the three.js Scene. If the objects property is specified, then building this array requires running query selectors and additional filtering.

By default with autoRefresh set to true, the raycaster component will automatically refresh this list when it detects entities or components are added and removed. While it is more friendly to auto-refresh, more advanced developers may want to disable autoRefresh and control when the raycaster is refreshed for performance.

To manually refresh the list of objects that the raycaster component tests against, call the .refreshObjects() method:

var raycasterEl = AFRAME.scenes[0].querySelector('[raycaster]');
raycasterEl.components.raycaster.refreshObjects();

A-Frame will call .refreshObjects() automatically when an entity is appended or detached from the scene, but it will not get called during normal DOM mutations (e.g., some entity changes its class).

Customizing the Line

If showLine is set to true, the raycaster will configure the line given the raycaster’s origin, direction, and far properties. To customize the line appearance provided by the showLine: true property, we configure the line component:

<a-entity raycaster="showLine: true; far: 100" line="color: orange; opacity: 0.5"></a-entity>

The line length is the raycaster’s far property when the raycaster is not intersecting any entity. By default, the far property defaults to 1000 meters meaning the line drawn will be 1000 meters long. When the raycaster intersects an object, the line will get truncated to the intersection point so it doesn’t shoot straight through.