Use collision tag for physics

[soraxas]

The collision tag in urdf should be used to calculate the physics, instead of visual
http://wiki.ros.org/urdf/Tutorials/Adding%20Physical%20and%20Collision%20Properties%20to%20a%20URDF%20Model

(I'm not sure if this is the best way to include both

• a visible (but non-colliding) mesh, and
• a non-visible (but colliding) mesh.

[rydb]

The collision tag in urdf should be used to calculate the physics, instead of visual http://wiki.ros.org/urdf/Tutorials/Adding%20Physical%20and%20Collision%20Properties%20to%20a%20URDF%20Model

(I'm not sure if this is the best way to include both

* a **visible** (but **non-colliding**) mesh, and

* a **non-visible** (but **colliding**) mesh

Thank you for the PR!

Could you see if you can your pr to work with the sample_robot_load.rs demo? The changes you added broke it.

Your PR:

This is what it should look like on load:

[soraxas]

That's because the current xml only contains collision tag and contains no visual tag. If the file is updated to be

�[32m�(B�[mdiff --git a/assets/model_pkg/urdf/diff_bot.xml b/assets/model_pkg/urdf/diff_bot.xml
index 437749a..c556099 100644
--- a/assets/model_pkg/urdf/diff_bot.xml
+++ b/assets/model_pkg/urdf/diff_bot.xml
@@ -6,9 +6,14 @@
         </inertial>
         <visual>
             <geometry>
                <mesh filename="package://model_pkg/models/base.obj"/>
             </geometry>
         </visual>
+        <collision>
+            <geometry>
+                <mesh filename="package://model_pkg/models/base.obj"/>
+            </geometry>
+        </collision>
     </link>
 
     <joint name="left_wheel_joint" type="continuous">
@@ -25,9 +30,14 @@
         </inertial>
         <visual>
             <geometry>
                <mesh filename="package://model_pkg/models/left_wheel_decimated.obj"/>
             </geometry>
         </visual>
+        <collision>
+            <geometry>
+                <mesh filename="package://model_pkg/models/left_wheel_decimated.obj"/>
+            </geometry>
+        </collision>
     </link>
 
     <joint name="right_wheel_joint" type="continuous">
@@ -44,9 +54,14 @@
         </inertial>
         <visual>
             <geometry>
                <mesh filename="package://model_pkg/models/right_wheel_decimated.obj"/>
             </geometry>
         </visual>
+        <collision>
+            <geometry>
+                <mesh filename="package://model_pkg/models/right_wheel_decimated.obj"/>
+            </geometry>
+        </collision>
     </link>
 
     <joint name="caster_wheel_joint" type="fixed">
@@ -66,6 +81,11 @@
                 <mesh filename="package://model_pkg/models/caster_wheel_decimated.obj"/>
             </geometry>
         </visual>
+        <collision>
+            <geometry>
+                <mesh filename="package://model_pkg/models/caster_wheel_decimated.obj"/>
+            </geometry>
+        </collision>
     </link>
 
 </robot>

then it will contains the original visual.

---

However, I came to a realisation that the current PR doesn't work as intended as the insertion of the geometry flag are getting overwritten; probably will need to insert separate entities to maintain both the visual and collision element.

[soraxas]

An example of a urdf is the following panda arm

<robot name="panda" xmlns:xacro="http://www.ros.org/wiki/xacro">
    <link name="panda_link0">
        <visual>
            <geometry>
                <mesh filename="package://robot_resources/panda/meshes/visual/link0.dae" />
            </geometry>
        </visual>
        <collision>
            <geometry>
                <mesh filename="package://robot_resources/panda/meshes/collision/link0.stl" />
            </geometry>
        </collision>
    </link>
    <link name="panda_link1">
        <visual>
            <geometry>
                <mesh filename="package://robot_resources/panda/meshes/visual/link1.dae" />
            </geometry>
        </visual>
        <collision>
            <geometry>
                <mesh filename="package://robot_resources/panda/meshes/collision/link1.stl" />
            </geometry>
        </collision>
    </link>
    <joint name="panda_joint1" type="revolute">
        <safety_controller k_position="100.0" k_velocity="40.0" soft_lower_limit="-2.8973" soft_upper_limit="2.8973" />
        <origin rpy="0 0 0" xyz="0 0 0.333" />
        <parent link="panda_link0" />
        <child link="panda_link1" />
        <axis xyz="0 0 1" />
        <limit effort="87" lower="-2.9671" upper="2.9671" velocity="2.3925" />
    </joint>
...

The visual tag is highly detailed: (the .dae file)

whereas the collision tag is a rough estimate: (the .stl file)

---

Using the visual tag for collision detection will makes it runs EXTREMELY slow