raycaster

Note: This documentation is for the old 0.6.0 version of A-Frame. Check out the documentation for the current 0.7.0 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
direction Vector3 coordinate of which direction the ray should point from relative to the entity’s origin. 0, 0, 0
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. 100
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 an entity. Event detail will contain el, the formerly intersected entity.

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>

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. A-Frame tries not to run this process too often (via the .refreshObjects() method) to save on 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.