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Merge pull request #629 from StanfordVL/fix/granular-system-collisions
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make GranularSystems not self-collidable to improve physics stability
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@ChengshuLi
ChengshuLi authored Mar 1, 2024
2 parents 6fdde6b + fb8295b commit a65e54a
Showing 1 changed file with 24 additions and 19 deletions.
43 changes: 24 additions & 19 deletions omnigibson/systems/micro_particle_system.py
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Original file line number Diff line number Diff line change
Expand Up @@ -628,6 +628,15 @@ def instancer_idns(cls):
"""
return [inst.idn for inst in cls.particle_instancers.values()]

@classproperty
def self_collision(cls):
"""
Returns:
bool: Whether this system's particle should have self collisions enabled or not
"""
# Default is True
return True

@classmethod
def initialize(cls):
# Create prototype before running super!
Expand Down Expand Up @@ -738,7 +747,6 @@ def generate_particles(
velocities=None,
orientations=None,
scales=None,
self_collision=True,
prototype_indices=None,
):
"""
Expand All @@ -753,15 +761,14 @@ def generate_particles(
active instancer that matches the requested idn, a new one will be created.
If None, this system will add particles to the default particle instancer
particle_group (int): ID for this particle set. Particles from different groups will automatically collide
with each other. Particles in the same group will have collision behavior dictated by @self_collision
with each other. Particles in the same group will have collision behavior dictated by
@cls.self_collision
velocities (None or np.array): (n_particles, 3) shaped array specifying per-particle (x,y,z) velocities.
If not specified, all will be set to 0
orientations (None or np.array): (n_particles, 4) shaped array specifying per-particle (x,y,z,w) quaternion
orientations. If not specified, all will be set to canonical orientation (0, 0, 0, 1)
scales (None or np.array): (n_particles, 3) shaped array specifying per-particle (x,y,z) scales.
If not specified, will be uniformly randomly sampled from (cls.min_scale, cls.max_scale)
self_collision (bool): Whether to enable particle-particle collision within the set
(as defined by @particle_group) or not
prototype_indices (None or list of int): If specified, should specify which prototype should be used for
each particle. If None, will randomly sample from all available prototypes
Expand Down Expand Up @@ -789,7 +796,6 @@ def generate_particles(
orientations=orientations,
scales=scales,
prototype_indices=prototype_indices,
self_collision=self_collision,
)
else:
inst.add_particles(
Expand All @@ -812,7 +818,6 @@ def generate_particle_instancer(
velocities=None,
orientations=None,
scales=None,
self_collision=True,
prototype_indices=None,
):
"""
Expand All @@ -825,7 +830,8 @@ def generate_particle_instancer(
delete / add additional ones at runtime during simulation. If None, this system will generate a unique
identifier automatically.
particle_group (int): ID for this particle set. Particles from different groups will automatically collide
with each other. Particles in the same group will have collision behavior dictated by @self_collision
with each other. Particles in the same group will have collision behavior dictated by
@cls.self_collision
positions (None or np.array): (n_particles, 3) shaped array specifying per-particle (x,y,z) positions.
If not specified, will be set to the origin by default
velocities (None or np.array): (n_particles, 3) shaped array specifying per-particle (x,y,z) velocities.
Expand All @@ -834,8 +840,6 @@ def generate_particle_instancer(
orientations. If not specified, all will be set to canonical orientation (0, 0, 0, 1)
scales (None or np.array): (n_particles, 3) shaped array specifying per-particle (x,y,z) scales.
If not specified, will be uniformly randomly sampled from (cls.min_scale, cls.max_scale)
self_collision (bool): Whether to enable particle-particle collision within the set
(as defined by @particle_group) or not
prototype_indices (None or list of int): If specified, should specify which prototype should be used for
each particle. If None, will use all 0s (i.e.: the first prototype created)
Expand Down Expand Up @@ -865,7 +869,7 @@ def generate_particle_instancer(
physx_particle_system_path=cls.system_prim_path,
particle_group=particle_group,
positions=np.zeros((n_particles, 3)) if positions is None else positions,
self_collision=self_collision,
self_collision=cls.self_collision,
fluid=cls.is_fluid,
particle_mass=None,
particle_density=cls.particle_density,
Expand Down Expand Up @@ -901,7 +905,6 @@ def generate_particles_from_link(
particle_group=0,
sampling_distance=None,
max_samples=5e5,
self_collision=True,
prototype_indices=None,
):
"""
Expand All @@ -923,13 +926,12 @@ def generate_particles_from_link(
active instancer that matches the requested idn, a new one will be created.
If None, this system will add particles to the default particle instancer
particle_group (int): ID for this particle set. Particles from different groups will automatically collide
with each other. Particles in the same group will have collision behavior dictated by @self_collision.
with each other. Particles in the same group will have collision behavior dictated by
@cls.self_collision.
Only used if a new particle instancer is created!
sampling_distance (None or float): If specified, sets the distance between sampled particles. If None,
a simulator autocomputed value will be used
max_samples (int): Maximum number of particles to sample
self_collision (bool): Whether to enable particle-particle collision within the set
(as defined by @particle_group) or not. Only used if a new particle instancer is created!
prototype_indices (None or list of int): If specified, should specify which prototype should be used for
each particle. If None, will randomly sample from all available prototypes
"""
Expand All @@ -943,7 +945,6 @@ def generate_particles_from_link(
particle_group=particle_group,
sampling_distance=sampling_distance,
max_samples=max_samples,
self_collision=self_collision,
prototype_indices=prototype_indices,
)

Expand All @@ -956,7 +957,6 @@ def generate_particles_on_object(
sampling_distance=None,
max_samples=5e5,
min_samples_for_success=1,
self_collision=True,
prototype_indices=None,
):
"""
Expand All @@ -977,8 +977,6 @@ def generate_particles_on_object(
max_samples (int): Maximum number of particles to sample
min_samples_for_success (int): Minimum number of particles required to be sampled successfully in order
for this generation process to be considered successful
self_collision (bool): Whether to enable particle-particle collision within the set
(as defined by @particle_group) or not. Only used if a new particle instancer is created!
prototype_indices (None or list of int): If specified, should specify which prototype should be used for
each particle. If None, will randomly sample from all available prototypes
Expand All @@ -993,7 +991,6 @@ def generate_particles_on_object(
sampling_distance=sampling_distance,
max_samples=max_samples,
min_samples_for_success=min_samples_for_success,
self_collision=self_collision,
prototype_indices=prototype_indices,
)

Expand Down Expand Up @@ -1414,6 +1411,14 @@ class GranularSystem(MicroPhysicalParticleSystem):

_particle_template = None

@classproperty
def self_collision(cls):
# Don't self-collide to improve physics stability
# For whatever reason, granular (non-fluid) particles tend to explode when sampling Filled states, and it seems
# the only way to avoid this unstable behavior is to disable self-collisions. This actually enables the granular
# particles to converge to zero velocity.
return False

@classmethod
def _clear(cls):
og.sim.remove_object(cls._particle_template)
Expand Down

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