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>