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    3D Model Creation

    In this chapter, we will assemble 3d model parts for visualization in Stellar X. In terms of applying to real workflow, we're going to assume that you finished your CAD design and have 3d model files for each links. If you are using manufactured robots, you should have your technical specification ready for DH-parameters, joint limits, physics property etc. This step is purely for visualization and optional, so you can skip it and have no problem moving forward. We'll be using 6-axis manipulator for this example. Please download 3d models from link below and unzip it.

    PS_A_03_500
    Rendered Image of Example Manipulator

    We'll be using blender for this step. Blender accepts most of major 3d model formats except some proprietary ones. You don't have to use blender, but the naming convention, model tree, output file format must be matched.

    1. Blender Preferences

    1. Stage

    blender
    • First, open blender and delete default Camera, Cube and Light.

    2. Naming Conventions

    Base

    Classification Name
    Joint J0
    Link link0

    Joint

    • J1 ~ Jn

    Link

    • link1 ~ linkn

    n increases with the number of joints.

    3. Create Joints

    blender blender
    • Click Add -> Empty -> Plain Axes to add axes. Add total of 7 axes and rename them to J0 ~ J7. These names act as joints in Designer and their name must be J{number}.
    blender blender blender
    • Now, we are going to add 3d models. Click File -> Import -> Wavefront. Go to saved directory and import all 7 of them. Be aware of import settings. If imported successfully, it should look like bottom picture.
    blender blender
    • Click link0 -> Rotation X and enter 0. The part should now stand up. Repeat this for all the other parts.

    Each link model must be moved under its corresponding joint.

    blender blender
    • Select link0 and shift-drag the link to the J0 joint. link0 should now lay under J0. Repeat it for all the other links.

    2. Hierarchical Structure

    The robot must be configured in a serial manipulator configuration.

    1. Basic Structure

    World
└── root
    └── links
        └── J0
            ├── link0
            └── J1
                ├── link1
                └── J2
                    ├── link2
                    └── J3
                        ├── link3
                        └── J4
                            ├── link4
                            └── J5
                                ├── link5
                                └── J6
                                    └── link6
    blender

    Select J1 and shift-drag to J0 joint. both J1 and link1 should now be under J0. Repeat same process for rest of the joints.

    2. Structure Description

    Item Description
    World 3D Tool Basic Scene
    root Robot Base Node
    links Joint Group
    J0~Jn Joint Nodes
    link0~linkn Link Model

    3. Precautions when Creating a Structure

    • All joints (Jn) must be set as children of the parent link.
    • Each link (linkn) must be set as a child of its corresponding joint (Jn).
    • If the hierarchy is incorrect, the robot structure will not function properly.

    3. Aligning DH Parameters with Model Structure

    The joint structure set in Blender must match the DH parameters in Stellar Designer.

    1. DH Parameter

    DH parameters are defined by transforming each joint coordinate system in the following order:

    Application order:

1. Z-axis rotation (θ)
2. Z-axis translation (d)
3. X-axis translation (a)
4. X-axis rotation (α)

This order cannot be changed and is the default rule for coordinate system calculations.

    2. Matching modeling and DH parameters in Blender

    blender
    • Shows the joint hierarchy in Blender.
    stellar
    • Shows the DH parameter settings for J1 in Stellar Designer.

    This means that J1 is transformed in the following order:

    1. No rotation about the Z-axis (θ = 0)
2. Translation of 205 mm along the Z-axis (d = 205)
3. No translation along the X-axis (a = 0)
4. No rotation about the X-axis (α = 0)

As a result, the coordinate frame of J2 is generated at a position
205 mm above J1 along the Z-axis.
    • Click J2 -> Location z and enter 0.205.
    • link2 and all the other links under J2 should move upward.
    blender blender blender
    • For J3, enter 0.27, and for J5, enter 0.23. Final result should look like bottom picture.

    When making your own robot, your parts may not align with the axes from DH-parameters. In that case, you have to adjust the position of the mesh itself from your CAD program. The base's position and joint positions when assembled should be { 0.0, 0.0, 0.0 } and 0, respectively.

    4. Setting Coordinate Axes and Rotation Axes

    • Set the rotation axis of each joint (Jn) based on the DH parameters.
    • Use rotation based on the Local Axis.
    • Do not use rotation based on the World Axis.

    stellar

    Robot Structure

    blender

    Blender

    5. Exporting Result

    1. Export Menu

    File → Export → glTF 2.0 (.glb/.gltf)

    blender

    2. Required Export Options

    Set the following in the Export window:

    Transform Settings

    +Y Up: Disabled

    This must be disabled to prevent coordinate transformation errors.

    blender

    And that should be it. For those who are having troubles, i'll leave download links for final assembly.

    .blend download link

    .glb download link

    6. Notes

    • Only .glb files are used in the final system.
    • Blender is a production example tool and is not a required tool.
    • The same structure and naming conventions must be maintained when using other tools.