How to add a STL file to the backend ?

[jordyBonnet]

Hello,

I'm able to use a robot that is not embedded by using its URDF file (and meshes) and making a class:

class MECA500(ERobot):
    def __init__(self, xacro_path):
        links, name, urdf_string, urdf_filepath = self.URDF_read(
            "meca_500_r3.urdf.xacro",
            tld=xacro_path,
        )
        super().__init__(
            links,
            name="MECA500",
            manufacturer="Mecademics",
            gripper_links=None,
            urdf_string=urdf_string,
            urdf_filepath=urdf_filepath,
        )
        # self.grippers[0].tool = SE3(0, 0, 0.1034)
        self.qr = np.array([0, 0, 0, 0, 0, 0])

Then when I want to view it in Swift, everything works fine with:

backend = Swift()
backend.launch()   # create graphical world
backend.add(m500) # add robot to the world
m500.q = m500.qr        # update the robot
backend.step()    # display the world

and we can add simple elements with spatialgeometry:

obstacle = SG.Cuboid([1, 1, 1])
backend.add(obstacle)

Ok 👍

But if I want to import some custom made 3D objects (which are not robots) I'm struggling a bit.

"Swift displays in a web browser table using three.js. At the moment it only works with models defined using URDF and can use STL or Collada meshes."

That means we also need to import the STL with a URDF file.
So I built one, with 2 objects inside:

<robot name="test_objects" xmlns:xacro="http://ros.org/wiki/xacro">
    <!-- Base link is the center of the robot's bottom plate -->
    <link name="first_obj_base_link">
            <visual>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <geometry>
                <mesh filename="C:/Users/jbonnet/Documents/3Dprinting/Surfu_2/syringe_pump/syringe_pump_case.stl" />
            </geometry>
            </visual>
            <collision>
            <origin xyz="10 0 0" rpy="0 0 0" />
            <geometry>
                <mesh filename="C:/Users/jbonnet/Documents/3Dprinting/Surfu_2/syringe_pump/syringe_pump_case.stl" />
            </geometry>
            </collision>
    </link>

    <link name="second_obj">
        <visual>
        <origin xyz="0 0 0" rpy="0 0 0" />
        <geometry>
            <mesh filename="C:/Users/jbonnet/Documents/3Dprinting/Surfu_2/syringe_pump/webcam_holder.stl" />
        </geometry>
        </visual>
        <collision>
        <origin xyz="10 10 0" rpy="0 0 0" />
        <geometry>
            <mesh filename="C:/Users/jbonnet/Documents/3Dprinting/Surfu_2/syringe_pump/webcam_holder.stl" />
        </geometry>
        </collision>
    </link>

    <joint name="first_obj_joint" type="fixed">
        <parent link="first_obj_base_link"/>
        <child link="second_obj"/>
        <origin xyz="0 0 0"/>
    </joint>

</robot>

Is this file ok ?
I also created a class asociated to it:

class Other_eltms(ERobot):
    def __init__(self, xacro_path):

        links, name, urdf_string, urdf_filepath = self.URDF_read(
            "test_obj.urdf.xacro",
            tld=xacro_path,
        )

        super().__init__(
            links,
            name="OE",
            manufacturer="OECompagny",
            gripper_links=None,
            urdf_string=urdf_string,
            urdf_filepath=urdf_filepath,
        )

        # self.grippers[0].tool = SE3(0, 0, 0.1034)
        self.qr = np.array([0])

The import works well, print gives me:

ERobot: OE (by OECompagny), 0 joints (), geometry
┌─────┬─────────────────────┬───────┬─────────────────────┬─────────────────────┐
│link │        link         │ joint │       parent        │ ETS: parent to link │
├─────┼─────────────────────┼───────┼─────────────────────┼─────────────────────┤
│   0 │ first_obj_base_link │       │ BASE                │                     │
│   1 │ @second_obj         │       │ first_obj_base_link │ SE3()               │
└─────┴─────────────────────┴───────┴─────────────────────┴─────────────────────┘

But when I want to use it in Swift with:

backend = Swift()
backend.launch()   # create graphical world
backend.add(m500) # add robot to the world
backend.add(others) # add 3D objects
m500.q = m500.qr        # update the robot
others.q = others.qr
backend.step()    # display the world

The web app says it encountered a problem (I have no other information except that it comes from backend.add(others) line)

Do you see something i'm doing wrong here ?
Does obstacle = SG.Cuboid([1, 1, 1]) create a urdf behind the scene ?

Suggestion:

• It could be nice to add a function to import STL files into Swift directly.
• for poeple that does not want to use low level functions, it could be nice to add some high level functions like move_linear ect...

PS: This work is awesome, Thanks a lot ! 👏

[jordyBonnet]

I just had to put the STL model into a folder inside the main working folder:
<mesh filename="meshes/syringe_pump_case.stl" scale="0.001 0.001 0.001" />

. . .

[gtreheux]

Hi @jordyBonnet,
are you using absolute or relative paths when creating an instance of the Meca500?