Blenderproc: About bop object physics positioning

[wangg12]

I tried the example of bop object physics positioning. I found that some objects like benchvise, lamp, duck, glue, can, driller, were always lying on the ground. I used the example config to render about 100 images, I could not find any image in which any of these objects was standing. What was the problem?

[ideas-man]

@wangg12 What do you mean by "standing"?
If I understood it correctly, then I would say that they are not supposed to.

    {
      "module": "object.ObjectPoseSampler",
      "config":{
        "objects_to_sample": {
          "provider": "getter.Entity",
          "conditions": {
            "cp_physics": True
          }
        },
        "pos_sampler":{
          "provider":"sampler.Uniform3d",
          "max":[0.2, 0.2, 0.6],
          "min":[-0.2, -0.2, 0.2]
        },
        "rot_sampler":{
          "provider":"sampler.UniformSO3"
        }
      }
    },
    {
      "module": "object.PhysicsPositioning",
      "config": {
        "min_simulation_time": 3,
        "max_simulation_time": 10,
        "check_object_interval": 1,
        "solver_iters": 25,
        "steps_per_sec": 100
      }
    },

These two modules are responsible for physics positioning and the resulting object pose depends on the outcome of running these two modules.

• object.ObjectPoseSampler samples poses for objects in a bounding box;
• object.PhysicsPositioning toggles a somewhat realistic physics animation - objects fall down.
  If you want to preserve the orientation of the object right after loading and just place them on the ground, then you may need to make some mods to the config file for sure. From the top of my head I would say that maybe try manipulators.EntityManipulator and just move the objects manually (or maybe look at the object.OnSurfaceSampler + sampler.UpperRegionSampler).

[wangg12]

For "standing", I mean the bottom of the object should be on the ground. I was just wondering, for the example in this repo, is it possible to get such standing poses for these objects? If so, what's the probability? In my observation, almost all of my rendered images didn't show such cases.

[MartinSmeyer]

Hi @wangg12 ! :-)
Objects are dropped onto the plane, maybe the title of the example is a bit misleading. For some objects the probability of staying upright is really small (however I certainly saw the duck and can upright before). If the goal is to generate a dataset for pose estimation with a bias towards upright objects, you could (1) select the initial poses to be upright before falling (rot_sampler in the config) (2) lower the dropping height (3) use the on_surface_sampler for placing the objects onto the plane before activating physics (4) reduce cube size --> physics --> increase cube size --> physics.

I guess (3) could make most sense to you?