Trying to set up simple Physics Scene; Failing Miserably

Omniverse General Discussion
1

I am consistently crashing Create, and I do not know why. I am running on an RTX 3070 Laptop w/ 8GB GPU Memory.
I am able to launch Create – all appears normal. I then try to create a simple physics scene with two blocks.
Here is a sample series of commands, with results:

  • create/Physics/groundplane – a plane appears
  • /create/shapes/cube – a cube appears. I drag it above the ground plane
  • Press Play – warning appears to add a Physics Scene, as expected
  • Create/Physics/Physics Scene – a PhysicsScene object appears in the Stage, as expected
  • Click ZeroGravity Icon – Zero Gravity Menu appears in Viewport, as expected
  • Just to be sure, I select the cube and move it around a little. It works fine.
  • Select CollisionMesh or GroundPlane by clicking on it and click “Set Static Marker” in Zero Gravity Menu. Ok so far?
  • Select Cube and move it around. It penetrates ground plane. I suppose this is correct, since I haven’t given the Cube any physics properties yet. (?)
  • Select Cube and “Set Dynamic Marker” using the ZeroGravity Menu.
  • Now I am unable to move the cube. I can select it but not move it.
  • If I unselect ZeroGravity, I am able to move the cube again. Is this normal?
  • Reselect Zero Gravity. Press Play. Nothing happens even though the cube is above the plane. Why doesn’t it fall?
  • I clear the markers from the cube. I can select and drag it now. But why?
  • I “Set Dynamic Marker” on the cube again. It is immobile. If I try to drag it, the xyz indicator snaps back to the cube. Press Play. Nothing happens.

If I keep playing around, the Create GUI usually crashes. What am I doing wrong? This is as simple as I can make it. Does anyone have a suggestion?

2

I have followed all the steps until “Now I am unable to move the cube. I can select it but not move it.” Up until that point everything is the same and its all correct and expected.

However, I am able to move the cube, I don’t have any problem doing that. Can you maybe post a video of you trying to do that and it not working?

Yes, if you deactivate zero gravity, it is again using the physics-less transform path, so it will now move again, that is expected.

Zero Gravity is not meant to be used together with pressing Play, those two modes are mutually exclusive.

Zero Gravity is meant for physics assisted placement of scene elements, it is not part of setting up physics for actual simulation. That is done differently. Please watch this for that:

Obviously the crashing part is not intended, that happens to me too, we will try to root cause it. Let me know if you find a 100% repro.

3

The most bizarre thing is that the Box-on-a-plane demo embedded in Create seems to work for me. I will post a video later with the exact repro.

I watched the wheel demo. For a raw beginner it is much too fast. Something simpler would be appreciated.

4

Here is a video of me trying to use ZeroGravity, and failing.

5

After more fiddling, it seems I can create objects that fall by another method. Here’s a video:

6

Hi,
ZeroGravity is a tool for objects placement in the scene. It does give the USD objects temporary physics properties. So once you exit the ZeroGravity, the objects loose any physics markup.

In the second video, thats the correct way how to add physics properties on prims in a scene, then if timeline is running they should be simulated.
Regards,
Ales

7

Yeah this zero gravity behavior is strange. Can you try doing all this stuff but:

  • Do NOT create a Physics/GroundPlane but rather just a Mesh Plane or a Box.
  • Do NOT press the play button.
  • Do NOT create a PhysicsScene.

Those steps are NOT necessary to use Zero Gravity, and while they should not be interfering with what you are doing, perhaps they are, somehow.