I have a player object (Matter/Sprite) and i want to add a bottom-sensor body in order to detect if the player hit the ground or a brick (enable jump for example).

i prepare the player body:

private preparePhysicsBody() {

    const bodyPlayer = this.scene.matter.bodies.rectangle(
      this.displayWidth / 2, this.displayHeight / 2,
      this.displayWidth, this.displayHeight);
    bodyPlayer.collisionFilter.category = PhysicsBodyCategories.PLAYER;
    bodyPlayer.collisionFilter.mask = PhysicsBodyCategories.WORLD;

    const bodyPlayerBottomSensor = this.scene.matter.bodies.rectangle(
      bodyPlayer.position.x, bodyPlayer.position.y + (this.displayHeight / 2),
      this.displayWidth - 6, 1, {
        isSensor: true
      });
    bodyPlayer.collisionFilter.category = PhysicsBodyCategories.PLAYER_BOTTOM;
    bodyPlayer.collisionFilter.mask = PhysicsBodyCategories.WORLD | PhysicsBodyCategories.BRICK;

    const body = this.scene.matter.body.create({
      parts: [
        bodyPlayerBottomSensor,
        bodyPlayer
      ]
    });
    this.setExistingBody(body);
    this.setFixedRotation();


    //on collisions
    this.setOnCollide((obj: MatterCollisionData) => {
      console.log(obj.bodyA.collisionFilter.category)
      console.log(obj.bodyB.collisionFilter.category)
    });

and a few bricks (also Matter/Sprite) in different positions:

class Brick extends Sprite {

  constructor(scene: Scene, x: number, y: number) {

    super(scene.matter.world, x, y, "brick", undefined, {
      isStatic: true
    });
    this.setPosition(x, y);
    this.setFriction(0.01)
    this.setDisplaySize(100, 10)
    this.setCollisionCategory(PhysicsBodyCategories.BRICK)

The first problem is, that the playerBody still collides with the bricks even though there is only the WORLD assigned to mask.

The second problem is, that setOnCollide doesn´t fire.

I tried also with the initial generated body of the playerObject and set the same values for category and mask and it worked, collision detection fired too.