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contact_particles

ContactParticles

Bases: RelativeObjectState, KinematicsMixin

Object state that handles contact checking between rigid bodies and individual particles.

Source code in omnigibson/object_states/contact_particles.py 
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class ContactParticles(RelativeObjectState, KinematicsMixin):
    """
    Object state that handles contact checking between rigid bodies and individual particles.
    """

    def _get_value(self, system, link=None):
        """
        Args:
            system (PhysicalParticleSystem): System whose contact particle info should be aggregated
            link (None or RigidPrim): If specified, the specific link to check for particles' contact

        Returns:
            set of int: Set of particle IDs in contact
        """
        # Make sure system is valid
        assert self.obj.scene.is_physical_particle_system(
            system_name=system.name
        ), "Can only get ContactParticles for a PhysicalParticleSystem!"

        # Variables to update mid-iteration
        contacts = set()
        idx = 0

        # Define callback function to use for omni's overlap_sphere() call
        def report_hit(hit):
            nonlocal link, idx
            link_name = None if link is None else link.prim_path.split("/")[-1]
            base, body = "/".join(hit.rigid_body.split("/")[:-1]), hit.rigid_body.split("/")[-1]
            continue_traversal = True
            # If no links are specified, then we assume checking contact with any link owned by this object
            # Otherwise, we check for exact match of link name
            if (link is None and base == self.obj.prim_path) or (link is not None and link_name == body):
                # Add to contacts and terminate early
                contacts.add(idx)
                continue_traversal = False
            return continue_traversal

        # Grab the relaxed AABB of this object or its link for coarse filtering of particles to ignore checking
        lower, upper = self.obj.states[AABB].get_value() if link is None else link.visual_aabb

        # Add margin for filtering inbound
        lower = lower - (system.particle_radius + m.CONTACT_AABB_TOLERANCE)
        upper = upper + (system.particle_radius + m.CONTACT_AABB_TOLERANCE)

        # Iterate over all particles and aggregate contacts
        positions = system.get_particles_position_orientation()[0]
        # Only check positions that are within the relaxed AABB of this object
        inbound_idxs = ((lower < positions) & (positions < upper)).all(dim=-1).nonzero()
        dist = system.particle_contact_radius + m.CONTACT_TOLERANCE
        for idx in inbound_idxs:
            og.sim.psqi.overlap_sphere(dist, positions[idx.item()].cpu().numpy(), report_hit, False)

        # Return contacts
        return contacts

    def _set_value(self, system, new_value):
        raise NotImplementedError("ContactParticles state currently does not support setting.")

    def _cache_is_valid(self, get_value_args):
        # Cache is never valid since particles always change poses
        return False

_get_value(system, link=None)

Parameters:

Name Type Description Default
system PhysicalParticleSystem

System whose contact particle info should be aggregated

 required
link None or RigidPrim

If specified, the specific link to check for particles' contact

 None

Returns:

Type Description
set of int

Set of particle IDs in contact
Source code in omnigibson/object_states/contact_particles.py 
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def _get_value(self, system, link=None):
    """
    Args:
        system (PhysicalParticleSystem): System whose contact particle info should be aggregated
        link (None or RigidPrim): If specified, the specific link to check for particles' contact

    Returns:
        set of int: Set of particle IDs in contact
    """
    # Make sure system is valid
    assert self.obj.scene.is_physical_particle_system(
        system_name=system.name
    ), "Can only get ContactParticles for a PhysicalParticleSystem!"

    # Variables to update mid-iteration
    contacts = set()
    idx = 0

    # Define callback function to use for omni's overlap_sphere() call
    def report_hit(hit):
        nonlocal link, idx
        link_name = None if link is None else link.prim_path.split("/")[-1]
        base, body = "/".join(hit.rigid_body.split("/")[:-1]), hit.rigid_body.split("/")[-1]
        continue_traversal = True
        # If no links are specified, then we assume checking contact with any link owned by this object
        # Otherwise, we check for exact match of link name
        if (link is None and base == self.obj.prim_path) or (link is not None and link_name == body):
            # Add to contacts and terminate early
            contacts.add(idx)
            continue_traversal = False
        return continue_traversal

    # Grab the relaxed AABB of this object or its link for coarse filtering of particles to ignore checking
    lower, upper = self.obj.states[AABB].get_value() if link is None else link.visual_aabb

    # Add margin for filtering inbound
    lower = lower - (system.particle_radius + m.CONTACT_AABB_TOLERANCE)
    upper = upper + (system.particle_radius + m.CONTACT_AABB_TOLERANCE)

    # Iterate over all particles and aggregate contacts
    positions = system.get_particles_position_orientation()[0]
    # Only check positions that are within the relaxed AABB of this object
    inbound_idxs = ((lower < positions) & (positions < upper)).all(dim=-1).nonzero()
    dist = system.particle_contact_radius + m.CONTACT_TOLERANCE
    for idx in inbound_idxs:
        og.sim.psqi.overlap_sphere(dist, positions[idx.item()].cpu().numpy(), report_hit, False)

    # Return contacts
    return contacts