Hi @lyx010318 and @jordan.thompson6560, I apologize for the very very late reply. The way to attach and detach deformables dynamically is to create attachments like with the script above and set those as inactive when you want them to detach.
It is not very scalable, but is the only way to do it without having to reset the Physics Simulation Context. Deleting a prim will cause Isaac Sim and Physics layer to go out of sync, so we only allow adding prims dynamically.
Here is a video of dynamically attaching and detaching a deformable:
The script for this is like this:
# Copyright (c) 2022-2024, NVIDIA CORPORATION. All rights reserved.
#
# NVIDIA CORPORATION and its licensors retain all intellectual property
# and proprietary rights in and to this software, related documentation
# and any modifications thereto. Any use, reproduction, disclosure or
# distribution of this software and related documentation without an express
# license agreement from NVIDIA CORPORATION is strictly prohibited.
#
from isaacsim import SimulationApp
simulation_app = SimulationApp({"headless": False})
from isaacsim.core.api import World
from isaacsim.core.utils.stage import create_new_stage
from pxr import UsdGeom, Gf, UsdPhysics, PhysxSchema
import math
from omni.physx.scripts import physicsUtils
from isaacsim.core.api.materials.deformable_material import DeformableMaterial
from isaacsim.core.prims import SingleDeformablePrim
def create_cylinder_mesh(radius=0.5, height=1.0, num_segments=16):
points, indices = [], []
for i in range(num_segments):
angle = 2 * math.pi * i / num_segments
x, y = radius * math.cos(angle), radius * math.sin(angle)
points.append(Gf.Vec3f(x, y, -height/2))
points.append(Gf.Vec3f(x, y, height/2))
bottom_center = len(points)
points.append(Gf.Vec3f(0, 0, -height/2))
top_center = len(points)
points.append(Gf.Vec3f(0, 0, height/2))
for i in range(num_segments):
ni = (i + 1) % num_segments
b0, b1 = i*2, ni*2
t0, t1 = i*2+1, ni*2+1
indices += [b0, t0, b1, t0, t1, b1]
for i in range(num_segments):
ni = (i + 1) % num_segments
indices += [bottom_center, i*2, ni*2]
indices += [top_center, ni*2+1, i*2+1]
return points, indices
create_new_stage()
stage = simulation_app.context.get_stage()
my_world = World(stage_units_in_meters=1.0, backend="torch", device="cuda")
my_world.scene.add_default_ground_plane()
my_world.reset()
UsdPhysics.Scene.Define(stage, "/physicsScene")
cylinder_radius, cylinder_height = 0.5, 1.0
overlap = cylinder_radius * 1.8
# Rigid cube
cube_path = "/World/Cube1"
cube = UsdGeom.Cube.Define(stage, cube_path)
cube.CreateSizeAttr(cylinder_height)
cube.AddTranslateOp().Set(Gf.Vec3f(0, 0, 0.75))
cube_rotate_op = cube.AddRotateXYZOp()
cube_rotate_op.Set(Gf.Vec3f(0, 0, 0))
cube_prim = cube.GetPrim()
UsdPhysics.CollisionAPI.Apply(cube_prim)
# Deformable cylinder
cyl_path = "/World/Cylinder2"
cyl_xform = UsdGeom.Xform.Define(stage, cyl_path)
mesh_path = cyl_xform.GetPrim().GetPath().AppendChild("cylinder").pathString
cyl_mesh = UsdGeom.Mesh.Define(stage, mesh_path)
pts, idxs = create_cylinder_mesh(cylinder_radius, cylinder_height, 16)
physicsUtils.set_or_add_translate_op(cyl_mesh, Gf.Vec3f(overlap, 0, 0.75))
cyl_mesh.GetPointsAttr().Set(pts)
cyl_mesh.GetFaceVertexIndicesAttr().Set(idxs)
cyl_mesh.GetFaceVertexCountsAttr().Set([3] * (len(idxs)//3))
mat = DeformableMaterial(prim_path=cyl_path + "/deformableMaterial", dynamic_friction=0.1, youngs_modulus=5e6, poissons_ratio=0.4, damping_scale=0.1, elasticity_damping=0.1)
deformable = SingleDeformablePrim(name="deformableCylinder2", prim_path=mesh_path, deformable_material=mat, self_collision=True)
my_world.scene.add(deformable)
attachment_counter = 0
def create_attachment():
global attachment_counter
attachment_counter += 1
att_path = mesh_path + f"/attachment_{attachment_counter}"
att = PhysxSchema.PhysxPhysicsAttachment.Define(stage, att_path)
att.GetActor0Rel().SetTargets([mesh_path])
att.GetActor1Rel().SetTargets([cube_path])
PhysxSchema.PhysxAutoAttachmentAPI.Apply(att.GetPrim())
print(f"Attachment {attachment_counter} created at time {my_world.current_time:.2f}s")
return att
my_world.reset()
attachments = [] # List of (attachment, creation_time) tuples
last_creation_time = -5.0 # Allow first attachment at 0.1s
try:
while simulation_app.is_running():
current_time = my_world.current_time
# Rotate cube slowly over time (10 degrees per second around Z-axis)
rotation_speed = 10.0 # degrees per second
rotation_angle = current_time * rotation_speed
cube_rotate_op.Set(Gf.Vec3f(0, 0, rotation_angle))
# Create new attachment every 5 seconds (starting at 0.1s)
if current_time >= 0.1 and current_time - last_creation_time >= 5.0:
att = create_attachment()
attachments.append((att, current_time))
last_creation_time = current_time
# Deactivate attachments after 2 seconds
for att, creation_time in attachments:
if current_time - creation_time >= 2.0 and att.GetPrim().IsActive():
att.GetPrim().SetActive(False)
print(f"Attachment deactivated at time {current_time:.2f}s (created at {creation_time:.2f}s)")
my_world.step(render=True)
except KeyboardInterrupt:
pass
finally:
simulation_app.close()
