How do I get the position of some components in Studio

🧑‍💻 Technical Support
1

This is a sample source code like ‘look at animation’,

I don’t really understand how “ecs.Position.get(world, component.eid)” works.

All results seem to point the same reference position.

import * as ecs from '@8thwall/ecs'  // This is how you access the ecs library.

ecs.registerComponent({
  name: 'face-to-camera',
  schema: {
    camera: ecs.eid,
    // Add data that can be configured on the component.
  },
  schemaDefaults: {
    // Add defaults for the schema fields.
  },
  data: {
    // Add data that cannot be configured outside of the component.
  },
  add: (world, component) => {
    // Runs when the component is added to the world.
  },
  tick: (world, component) => {
    // Runs every frame.ß
  	const {camera} = component.schema
  	if (!camera) {
  		console.warn('Camera entity not set in portalHiderController')
  		return
  	}
    // https://www.8thwall.com/tutorials/guides/western-memory
    // console.log('tick0', component.eid, camera)

    //
    const p1 = ecs.Position.get(world, component.eid)
    console.log('tick 1', p1)
    const p1v3 = ecs.math.vec3.from(p1)

    const p2 = ecs.Position.get(world, camera)
    console.log('tick 2', p2)
    const p2v3 = ecs.math.vec3.from(p2)


    // p1V3 and p2V3 are defferent << It's OK
    // but p1 and p2 are same value << ???
    console.log('tick 3', p1, p2, p1v3, p2v3)

    ////
    const p3 = ecs.Position.get(world, component.eid)
    const p4 = ecs.Position.get(world, camera)

    // same results. I am confused.
    console.log('tick 4', p1, p2, p3, p4)

    const q = ecs.math.quat.lookAt(p2v3, p1v3, ecs.math.vec3.xyz(0, 1, 0))
    // console.log('tick q', p1v3, p2v3, q)

    ecs.Quaternion.set(world, component.eid, q)
  },
  remove: (world, component) => {
    // Runs when the component is removed from the world.
  },
})
2

ecs.Position.get gives you the local position.

If you want the world position you’ll need to do:

const matrix = ecs.math.mat4.i()
world.getWorldTransform(eid, matrix)
const worldPosition = ecs.math.vec3.zero()
matrix.decomposeT(worldPosition)

console.log(worldPosition)

We’re working on making this easier. :slight_smile:

Also check out this documentation page related to one of the “gotcha’s” around cursors:

1 Like
3

Thank you for your kindness. I understand.