How to affect objects with force fields

Omniverse Isaac Sim
1

Isaac Sim Version

4.5.0
4.2.0
4.1.0
4.0.0
4.5.0
2023.1.1
2023.1.0-hotfix.1
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Operating System

Ubuntu 22.04
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GPU Information

  • Model: RTX 6000 Ada
  • Driver Version: 575.57.08

Topic Description: How to affect objects with force fields?

Detailed Description

I’ve opened up one of the demos from the Force Fields extension. I’m trying to apply the force to new objects I add to the scene, but it doesn’t seem to be working.

Steps to Reproduce

  1. Enable Force Fields extension
  2. Open Physics Demo Scenes → Force Fields → Explode demo
  3. Add a sphere
  4. On the sphere, Add → Physics → Colliders Preset
  5. Press play
  6. Sphere simply drops from gravity, is not affected by the force field :(

Screenshots or Videos

By the way, the USD file is sideways and everything is scaled by 100. I guess it was created before Isaac Sim changed the convention to Z-up and meters.

I’ve attached the USD file below if anyone can help me figure out what’s wrong.
sphere_not_affected_by_explode_demo.usd.zip (4.2 KB)

2

@ajong USD orientation aside, which appears to be what the source code has defined for the demo, what you will need to make the manually created sphere be influenced by the forces in the scene is to make sure you have the following:

  • Collider
  • Rigid Body
  • Mass

you can add the first two through Add > Physics > Rigid Body with Colliders Preset, and only when you have either collider or rigidbody, mass will show up in the Add > Physics menu. you were really close!

and once you have mass, you will want to set the Density to 1.0 if you wish to have the same behavior as the boxes in the demo.

image
image658×420 19.6 KB

after you have the above defined, you should be able to run the simulation to see the sphere get sucked up before ‘exploded’ along with the rest of the boxes.

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3

Whoa! That worked, thank you @Simplychenable .

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4

Does density always have to be manually set for the force fields to work?

5

manually? not at all. Below is a snippet to set density programmatically:

import isaacsim.core.utils.stage as stage_utils
from isaacsim.core.prims import SingleRigidPrim

# create a Cube at the given path
stage_utils.get_current_stage().DefinePrim("/World/Xform", "Xform")
stage_utils.get_current_stage().DefinePrim("/World/Xform/Cube", "Cube")

# wrap the prim as rigid prim
prim = SingleRigidPrim("/World/Xform/Cube")
prim.set_density(1.0)

here’s a bit more context on issacsim.core.prim API for SingleRigidPrim:

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