Incorrect collision detection causes strange rigid body floating

[Linmin1209]

I am currently using Genesis to simulate a robotic arm performing a block assembly task. However, I’ve encountered a strange issue: after importing the blocks into the environment, they seem to float up and down erratically on the surface of the rigid body.

This behavior makes it challenging to achieve stable interactions in the simulation. I suspect it might be related to incorrect collision detection or physics settings.

2025-01-02.172131.mp4

The blocks were imported using 3D files in the .obj format, and I’ve checked the collision meshes using visualization tools—they appear to be perfectly normal.

Could you please provide guidance on how to resolve this issue or suggest possible configurations to investigate?

[zhouxian]

Oh by default, we convexify all the geoms

could you use vis_mode=‘collision’ when adding entity to visualize the collision geoms?

[Linmin1209]

Thank you for your reply. When I use vis_mode="collision", the result is like this.

[ZhiyuanZhou8]

Hi, thanks for your great work!
I want to ask how to set such a desk in the scene. By using .urdf?

[zhouxian]

The collision mesh looks fine

can you share your script? are u using convex decomposition or sdf for nonconvex obj?

Also one tip: when there's multiple objects, turning on contact island (in rigid_options) could greatly improve speed

[Linmin1209]

@ZhiyuanZhou8 Yeah, I use the asset from PartNet Dataset.

[Linmin1209]

@zhouxian Thank you for your tips. And, here is my script:

import genesis as gs
import numpy as np
import time
import json
from PIL import Image

gs.init(backend=gs.vulkan,precision='32')

scene = gs.Scene(show_viewer=True,
                 viewer_options = gs.options.ViewerOptions(
                    res           = (1280, 960),
                    camera_pos    = (3.5, 0.0, 2.5),
                    camera_lookat = (0.0, 0.0, 0.5),
                    camera_fov    = 40,
                    max_FPS       = 60
                ),
                vis_options = gs.options.VisOptions(
                    show_world_frame = True,
                    world_frame_size = 1.0,
                    show_link_frame  = False,
                    show_cameras     = False,
                    plane_reflection = True,
                    ambient_light    = (0.1, 0.1, 0.1),
                ),
                rigid_options= gs.options.RigidOptions(
                    enable_self_collision=True
                ),
                # renderer=gs.renderers.Rasterizer(),
                renderer = gs.renderers.RayTracer())

plane = scene.add_entity(gs.morphs.Plane(collision=True))

cam = scene.add_camera(
    res    = (1280, 960),
    pos    = (3.5, 0.0, 2.5),
    lookat = (0, 0, 0.5),
    fov    = 30,
    GUI    = False,
)

with open("./FMB/assets/scenes/scene1/scene_table.json","r")as f:
# with open("./FMB/assets/scenes/scene1/scene1.json","r")as f:
    scene_data = json.load(f)

scene_dict = {}
for i in scene_data: 
    if i["type"] == "urdf":
        obj = scene.add_entity(
        gs.morphs.URDF(**i["attribute"])
    )
    else:
        obj = scene.add_entity(
            gs.morphs.Mesh(**i["attribute"]),
            vis_mode="collision"
        )
      
    scene_dict[i["name"]] = obj
scene.build()
while True:
    # time.sleep(5)
    scene.step()

And the json file is:

[
    {
    "name":"robot",
    "type": "urdf",
    "attribute":
    {
    "file":"./FMB/assets/robots/gen3.urdf",
    "pos":[0.20,0.40,1.248],
    "euler":[0,0,90],
    "fixed": true,
    "merge_fixed_links": false 
    }
},
    {
    "name":"blue",
    "type": "mesh",
    "attribute":
    {
    "file":"./FMB/assets/scenes/scene1/blue.obj",
    "pos":[0.20,0,1.248],
    "euler":[90,0,0],
    "convexify": false,
    "decompose_nonconvex": false
    }
},
    {
    "name":"green",
    "type": "mesh",
    "attribute":
    {
    "file":"./FMB/assets/scenes/scene1/green.obj",
    "pos":[0.20,0,1.249],
    "euler":[90,0,0],
    "convexify": false,
    "decompose_nonconvex": false
    }
},
    {
    "name":"purple",
    "type": "mesh",
    "attribute":
    {
    "file":"./FMB/assets/scenes/scene1/purple.obj",
    "pos":[0.20,0,1.249],
    "euler":[90,0,0],
    "convexify": false,
    "decompose_nonconvex": false
    }
},
    {
    "name":"red_board",
    "type": "mesh",
    "attribute":
    {
    "file":"./FMB/assets/scenes/scene1/red.obj",
    "pos":[0.20,0,1.249],
    "euler":[90,0,0],
    "convexify": false,
    "decompose_nonconvex": false
    }
},
    {
    "name":"yellow",
    "type": "mesh",
    "attribute":{
    "file":"./FMB/assets/scenes/scene1/yellow.obj",
    "pos":[0.20,0,1.249],
    "euler":[90,0,0],
    "convexify": false,
    "decompose_nonconvex": false
    }
},
    {
    "name":"tool",
    "type": "mesh",
    "attribute":
    {
    "file":"./FMB/assets/scenes/scene1/tool.obj",
    "pos":[0.20,0,1.248],
    "euler":[90,0,0],
    "convexify": false,
    "decompose_nonconvex": false
    }
},
    {
    "name":"table",
    "type": "urdf",
    "attribute":
    {
    "file":"./FMB/assets/tables/table_01/mobility.urdf",
    "pos":[0.20,0,0.8047],
    "euler":[0,0,0],
    "fixed": true
    }
}
]

I set the convexify=False and decompose_nonconvex=False.