Unrealistic Mesh Penetration between Panda Gripper and Plate

[ashvinar]

Hi,

I'm seeing unrealistic penetration between the panda gripper and plate. Do you know what is going on here and is there any way to fix it?
@jstmn

Screencast.from.2025-11-06.16-45-36.webm

[StoneT2000]

how is the object built? Can you share the load_scene code? This is a non-convex mesh, for thin shapes penetration can occur sometimes depending on how you load the object at times.

[ashvinar]

heres the code:

def _load_scene(self, options: Dict):
self.table_scene = TableSceneBuilder(
env=self, robot_init_qpos_noise=self.robot_init_qpos_noise
)
self.table_scene.build()

    self.plate = self._build_plate()
    self.dish_rack = self._build_rack()
    self.plate_support = self._build_plate_support()

def _build_plate(self):
    """Build a plate with a raised rim using simple analytic geometry."""
    builder = self.scene.create_actor_builder()

    # Physical material with maximum friction to prevent slipping during rotation
    physical_material = PhysxMaterial(
        static_friction=20.0,
        dynamic_friction=20.0,
        restitution=0.0
    )

    outer_radius = self._plate_outer_radius
    inner_radius = self._plate_inner_radius
    wall_thickness = outer_radius - inner_radius
    base_thickness = self._plate_base_thickness
    rim_height = self._plate_rim_height
    total_height = self._plate_total_height
    density = self._plate_density

    bottom_z = -total_height / 2.0
    base_center_z = bottom_z + base_thickness / 2.0
    rim_center_z = bottom_z + base_thickness + rim_height / 2.0
    rim_half_height = rim_height / 2.0

    # Use your STL for collision with the same scale as visual
    collision_scale = 0.0025
    builder.add_nonconvex_collision_from_file(
        filename=str(self._plate_visual_mesh_path),
        scale=[collision_scale, collision_scale, collision_scale],
        pose=sapien.Pose(),
        material=physical_material,
        density=density,
    )

    # Use the plate STL mesh for visual
    # Make it bright and solid so it's clearly visible
    plate_visual_material = sapien.render.RenderMaterial(
        base_color=[0.98, 0.95, 0.90, 1.0],  # Bright off-white
        specular=0.6,
        roughness=0.25,
        metallic=0.0,
    )

    # Add scaled visual mesh - the STL is very large, scale it down dramatically
    # Scale to match our outer_radius of 0.04m (40mm)
    visual_scale = 0.0025  # Start with 1mm units, adjust as needed
    builder.add_visual_from_file(
        filename=str(self._plate_visual_mesh_path),
        scale=[visual_scale, visual_scale, visual_scale],
        pose=sapien.Pose(p=[0, 0, 0.001]),  # Lift visual 1mm to avoid clipping
        material=plate_visual_material,
    )

    builder.initial_pose = sapien.Pose()
    # Build as dynamic so it can be grasped
    return builder.build(name="plate")