Gazebo doesn't display meshlab scaled models and doesn't show any error

Darkproduct commented 3 years ago

TLDR:

Scaling any .obj mesh with meshlab will make it not visible without any error output even with --verbose.

Steps to reproduce:

Creating the model

I`m using this simple stone model: https://sketchfab.com/3d-models/rock-stone-02-0455747c7ac848269830ed0dca33726c

After downloading, extracting and some renaming my folder structure looks like this:

.
├── meshes
│   ├── stone_01.mtl
│   └── stone_01.obj
├── model.config
├── model.sdf
└── textures
    ├── stone_01.jpg
    ├── stone_01_normal.jpg
    └── stone_01_occlusion.jpg

model.sdf:

<?xml version="1.0" ?>
<sdf version="1.6">
  <model name='Stone_01'>
    <pose frame=''>0 0 0.2 0 -0 0</pose>
    <static>true</static>
    <allow_auto_disable>true</allow_auto_disable>
    <link name='Stone_01_link'>
      <collision name='collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <box>
            <!-- TODO: Better collision box. Maybe an ultra low poly rock. -->
            <size>1.516384 0.974134 0.495299</size>
          </box>
        </geometry>
        <max_contacts>10</max_contacts>
      </collision>
      <visual name='visual'>
        <geometry>
          <mesh>
            <uri>model://stone_01/meshes/stone_01.obj</uri>
            <scale>1 1 1</scale>
          </mesh>
        </geometry>
        <material>
          <!--<shader type="normal_map_object_space">
          <shader type="normal_map_tangent_space">
            <normal_map>model://stone_01/textures/stone_01_normal.jpg</normal_map>
          </shader>-->
          <pbr>
            <metal>
              <albedo_map>model://stone_01/textures/stone_01.jpg</albedo_map>
              <ambient_occlusion_map>model://stone_01/textures/stone_01_occlusion.jpg</ambient_occlusion_map>
              <normal_map type="tangent">model://stone_01/textures/stone_01_normal.jpg</normal_map>
            </metal>
          </pbr>
        </material>
      </visual>
    </link>
  </model>
</sdf>

Loading the original model

The stone will be loadable with its texture, but I'm not sure if the ambient_occlusion_map and the normal_map is working properly. But still. There is a model with texture. stone Output from starting with rosrun gazebo_ros gazebo --verbose and adding the model from the insert tab.

Gazebo multi-robot simulator, version 11.4.0
Copyright (C) 2012 Open Source Robotics Foundation.
Released under the Apache 2 License.
http://gazebosim.org

[ INFO] [1617629722.264775503]: Finished loading Gazebo ROS API Plugin.
[ INFO] [1617629722.267743523]: waitForService: Service [/gazebo/set_physics_properties] has not been advertised, waiting...
[Msg] Waiting for master.
[Msg] Connected to gazebo master @ http://127.0.0.1:11345
[Msg] Publicized address: 192.168.178.112
[Msg] Loading world file [/usr/share/gazebo-11/worlds/empty.world]
[ INFO] [1617629722.603234672, 0.010000000]: waitForService: Service [/gazebo/set_physics_properties] is now available.
[ INFO] [1617629722.628483938, 0.034000000]: Physics dynamic reconfigure ready.

Scaling the model

Scaling with meshlab. Load the .obj file into meshlab. Use Filters ⇒ Normals, Curvatures and Orientation ⇒ Transform: Scale, Normalize. Change the values for each axis (I used 0.5 on each) and click apply. Now go to File ⇒ Export Mesh… and hit ok.

Loading the scaled model

Trying to load the .obj file now will result in nothing, but you'll be able to select it which shows an empty bounding box: Output from starting with rosrun gazebo_ros gazebo --verbose and adding the model from the insert tab.

Gazebo multi-robot simulator, version 11.4.0
Copyright (C) 2012 Open Source Robotics Foundation.
Released under the Apache 2 License.
http://gazebosim.org

[ INFO] [1617632110.687954177]: Finished loading Gazebo ROS API Plugin.
[ INFO] [1617632110.689942239]: waitForService: Service [/gazebo/set_physics_properties] has not been advertised, waiting...
[Msg] Waiting for master.
[Msg] Connected to gazebo master @ http://127.0.0.1:11345
[Msg] Publicized address: 192.168.178.112
[Msg] Loading world file [/usr/share/gazebo-11/worlds/empty.world]
[ INFO] [1617632111.023999576]: waitForService: Service [/gazebo/set_physics_properties] is now available.
[ INFO] [1617632111.055724540, 0.014000000]: Physics dynamic reconfigure ready.

The new mesh will still be loadable by meshlab and other 3D applications.

What I tried:

Using the mesh for the collision as well. This has the same effect as in the visual layer. Nothing is shown there with the scaled model.
Exports from the unloadable model to .stl or .dae will load in gazebo

I'm using Ubuntu 20.04 LTS with ROS Noetic, Gazebo 11.4.0, MeshLab_64bit_fp v2020.03+dfsg1.

newcanopies commented 3 years ago

@Darkproduct you might find some clues if you compare the original to the meshlab-scaled .OBJ mesh in a text editor.

meshlab could be introducing an encoding change to the obj file, or is handling the SCALE argument infitesimaly. does meshlab use Meters (gazebo unit) or centimeters?

mintar commented 1 year ago

I've debugged this and found a solution. You have to edit your .mtl file.

The Blender-generated file (working in Gazebo) has this line:

d 1.0

The Meshlab-generated file (broken in Gazebo) has this line:

Tr 1.000000

This defines transparency, see Wikipedia:

Materials can be transparent. This is referred to as being dissolved. Unlike real transparency, the result does not depend upon the thickness of the object. A value of 1.0 for "d" is the default and means fully opaque, as does a value of 0.0 for "Tr". Dissolve works on all illumination models.

# some implementations use 'd'
d 0.9
# others use 'Tr' (inverted: Tr = 1 - d)
Tr 0.1

In other words, the Meshlab export specifies full transparency, which Gazebo correctly renders as "invisible".

Solution: Remove the "Tr 1.000000" line (or better yet, copy the complete lines from the original Blender file) and the error is fixed.

gazebosim / gazebo-classic