Creating moving objects using python scripts

Omniverse Isaac Sim
1

Hi
I am trying to create a simulation environment with moving objects. In this case, I try to spawn a cylinder in the sim and give it some initial angular_velocity so that it moves a bit and slows down. I want these natural physics because I would like to add a robot to the scene as well so that it can interact with the object.

But when I run the simulation, the cylinder does not move at all. What could I do to get it moving in the standalone python script?

from omni.isaac.kit import SimulationApp

simulation_app = SimulationApp({"headless": False})

import argparse
import sys

import carb
import numpy as np

from omni.isaac.core import World
from omni.isaac.core.utils.nucleus import get_assets_root_path
from omni.isaac.core.objects import DynamicCylinder
from omni.isaac.core.materials.physics_material import PhysicsMaterial

parser = argparse.ArgumentParser()
parser.add_argument("--test", default=False, action="store_true", help="Run in test mode")
args, unknown = parser.parse_known_args()


assets_root_path = get_assets_root_path()
if assets_root_path is None:
    carb.log_error("Could not find Isaac Sim assets folder")
    simulation_app.close()
    sys.exit()

my_world = World(stage_units_in_meters=1.0)
my_world.scene.add_default_ground_plane()

prim = DynamicCylinder(
    prim_path="/World/Xform/Cylinder",
    name="dynamic_cylinder",
    position=np.array([0.0, 0.0, 0.1]),
    orientation=np.array([1 / np.sqrt(2), 1 / np.sqrt(2), 0.0, 0.0]),
    radius=0.1,
    height=1.0,
    color=np.array([1.0, 0.0, 0.0]),
    mass=1.0
)
material = PhysicsMaterial(
    prim_path="/World/physics_material/aluminum",  # path to the material prim to create
    dynamic_friction=0.1,
    static_friction=0.1,
    restitution=0.1
)

i = 0
while simulation_app.is_running():
    print("#########################################################")
    my_world.step(render=True)
    if my_world.is_playing():
        print("ITERATION : ", i)
        i += 1
        if my_world.current_time_step_index == 0:
            my_world.reset()
        # position = cube.get_local_pose()[0]
        # position[0] += 0.005
        # cube.set_local_pose(position)
            if i>=60:
                prim.set_linear_velocity(angular_velocity=np.array([10.0, 0.0, 0.0]))
        observations = my_world.get_observations()
        print(prim.get_angular_velocity())
    if args.test is True:
        break


simulation_app.close()
2

Hi @rohanb27 - Have you looked at this document?, this covers topic about how to move the robot.
https://docs.omniverse.nvidia.com/isaacsim/latest/core_api_tutorials/tutorial_core_hello_robot.html#move-the-robot

3

This provides methods to move robots which are articulations. If I wanted to move / apply force on an object, such as a cylinder, using a standalone script then how can I do that? (this might be helpful if I want to introduce perturbations while simulating a robot in a household task)

6

Don’t you have code logic issue in your snippet?
Try printing more variables to see how different indices you used are changing depending on the timeline events like when you hit play and so on
for example try something like this, which should apply a linear velocity the first time you hit play

i = 0
while simulation_app.is_running():
    print("#########################################################")
    my_world.step(render=True)
    if my_world.is_playing():
        print("ITERATION : ", i)

        if my_world.current_time_step_index == 0:
            my_world.reset()

        if i==0:
            prim.set_linear_velocity(np.array([0.0, 1.0, 0.0]))    
            i += 1	

        observations = my_world.get_observations()
        print(prim.get_angular_velocity())
    if args.test is True:
        break