[BUG] Mismatch between visualization and URDF

[SimonXie2004]

Hi! I have encountered and identified a bug that causes mismatch between generated visualization and actual exported URDF. For those using URDFormer as comparison experiments, this might be a issue.

Here's the explanation:

Content:

1. Problem Description
2. The (possible) code that causes this bug

Problem Description

I have used case: StorageFurniture_45717, view 07 from partnet dataset as input. Here's the rendered result (direct output of running demo.py) :

However, the exported URDF looks like the following.

The URDF is as follows

<?xml version='1.0' encoding='utf-8'?>
<robot name="my_urdf">
    <link name="base_link">
        <visual>
            <origin xyz="0 0 0" rpy="0.0 0.0 0.0" />
            <material name="white">
                <color rgba="0.8 0.8 0.8 1" />
            </material>
            <geometry>
                <mesh filename="../meshes/cabinet.obj" scale="1 1 1" />
            </geometry>
        </visual>
        <collision>
            <origin xyz="0 0 0" rpy="0.0 0.0 0.0" />
            <geometry>
                <mesh filename="../meshes/cabinet.obj" scale="1 1 1" />
            </geometry>
        </collision>
        <inertial>
            <mass value="1" />
            <inertia ixx="1e-4" ixy="0" ixz="0" iyy="1e-4" iyz="0" izz="1e-4" />
        </inertial>
    </link>
    <link name="doorL0">
        <visual>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <material name="white">
                <color rgba="0.8 0.8 0.8 1" />
            </material>
            <geometry>
                <mesh filename="../meshes/parts/doorL.obj" scale="1 3.99 3.99" />
            </geometry>
        </visual>
        <collision>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <geometry>
                <mesh filename="../meshes/parts/doorL.obj" scale="1 3.99 3.99" />
            </geometry>
        </collision>
        <inertial>
            <mass value="0.2" />
            <inertia ixx="1e-4" ixy="0" ixz="0" iyy="1e-4" iyz="0" izz="1e-4" />
        </inertial>
    </link>
    <joint name="doorL0_to_base_link" type="revolute">
        <axis xyz="0 0 1" />
        <limit effort="5" lower="-1.57" upper="0" velocity="2.283" />
        <origin xyz="0 0.0 0.0" rpy="0.0 0.0 0.0" />
        <parent link="base_link" />
        <child link="doorL0" />
    </joint>
    <link name="knob1">
        <visual>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <material name="white">
                <color rgba="0.8 0.8 0.8 1" />
            </material>
            <geometry>
                <mesh filename="../meshes/parts/knob.obj" scale="1 1 1" />
            </geometry>
        </visual>
        <collision>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <geometry>
                <mesh filename="../meshes/parts/knob.obj" scale="1 1 1" />
            </geometry>
        </collision>
        <inertial>
            <mass value="0.2" />
            <inertia ixx="1e-4" ixy="0" ixz="0" iyy="1e-4" iyz="0" izz="1e-4" />
        </inertial>
    </link>
    <joint name="knob1_to_doorL0" type="fixed">
        <axis xyz="1 0 0" />
        <limit effort="5" lower="0" upper="1.57" velocity="2.283" />
        <origin xyz="0 0.8333333333333334 0.16666666666666666" rpy="0.0 0.0 0.0" />
        <parent link="doorL0" />
        <child link="knob1" />
    </joint>
</robot>

However, in this URDF, there is no actually ../mesh/oven.obj, which is the following image (that should belong to this mesh)

Possible code that causes this bug

In <repo_root>/utils.py, Line 385-397:

part_names = ['none', 'drawer', 'doorL', 'doorR',
                  'handle', 'knob', 'washer_door', 'doorD', 'oven_door', 'doorU']
    base_names = ['none', 'cabinet_kitchen', 'oven', 'dishwasher', 'washer', 'fridge',
                  'oven_fan', 'shelf_base'
                  ]
    part_path = "meshes/parts/"

    # fix the oven fan problem: if there are parts, root shouldn't be oven fan
    if len(position_pred_ori) > 1 and mesh_base == 6:
        mesh_base = 1


    root = "meshes/{}.obj".format(base_names[mesh_base])

This has actually extracted the base_link from class URDFormer's forward() result. (Note that mesh_base is a return value from URDFormer's forward.)

However, in <repo_root>/utils.py, Line 610:

        write_urdfs(filename, root, root_scale, root_position, root_orientation, links, link_scales, link_positions,
                link_orientations, linkparents, jointtypes, linkJointAxis)

In this function, root is actually not used. Hence, the root_link is actually not exported to the URDF.

This might explain why the oven.obj is missing from the exported URDF.