Blender Workflow for Cleaning CAD Meshes for ROS 2 / Gazebo¶

Use this workflow to convert raw CAD exports into clean simulation meshes that render correctly and run faster.

By the end, you should have:

one clean visual mesh (.dae or .obj)
one simplified collision mesh (.stl)
a URDF-ready mesh setup with fewer simulation issues

Quick Start¶

Import mesh into Blender.
Clean geometry (By Distance, normals, triangulation).
Decimate for visual mesh and apply transforms.
Create a heavily simplified collision copy.
Export visual and collision meshes, then reference both in URDF.

Expected result:

no missing faces in Gazebo
consistent scale and orientation
faster simulation and stable collisions

Tip

Keep your visual and collision meshes separate. This gives better performance and more stable physics than reusing one heavy mesh for both.

Prerequisites¶

Item	Requirement
Source model	CAD export (`.obj`, `.stl`, or `.dae`)
Blender	Any recent version with Decimate modifier
Target stack	ROS 2 + URDF + Gazebo
Goal	visual quality and simulation stability

Workflow Overview¶

Typical pipeline:

CAD (Onshape / SolidWorks)
        v
Export STEP / OBJ
        v
Blender cleanup
        v
Visual mesh (.dae / .obj)
Collision mesh (.stl)
        v
URDF
        v
ROS 2 + Gazebo

Step-by-Step¶

1) Import and identify the mesh¶

Start Blender.
Go to File -> Import.
Import your mesh file (.dae, .stl, .obj).
In the Outliner, select the object with the triangle icon.

Example Outliner:

Collection
 └ robot_part

Expected result:

correct mesh object is selected
object is visible in the viewport

2) Enter edit mode and select all geometry¶

With the mesh selected:

Tab
A

Or use:

Object Mode -> Edit Mode

Expected result:

all vertices/edges/faces are selected
you can edit the full mesh at once

3) Remove duplicate vertices¶

CAD exports often contain overlapping vertices.

Use:

M -> By Distance

Example message:

Removed 12000 vertices

Expected result:

cleaner topology
fewer non-manifold artifacts later

4) Fix normals and orientation¶

Recalculate normals:

Shift + N

Enable face orientation overlay:

Viewport Overlays -> Face Orientation

Interpret colors:

Blue = correct outward face
Red = flipped face

If needed, flip selected incorrect faces:

Alt + N -> Flip

Expected result:

outer surfaces are mostly blue
no random face disappearance in Gazebo

Warning

Do not skip normal checks. Flipped normals are a common cause of missing surfaces in simulation.

5) Triangulate and reduce polygon count¶

Triangulate:

A
Ctrl + T

Apply decimation for the visual mesh:

Add Modifier -> Decimate
Ratio: 0.2 - 0.4

Example:

1,200,000 faces -> 40,000 faces

Expected result:

all faces are triangles
visual mesh is lighter but still acceptable

6) Apply object transforms¶

Return to object mode and apply transforms:

Tab
Ctrl + A -> Rotation & Scale

Expected result:

scale and orientation are normalized
URDF and Gazebo import behavior is consistent

7) Export the visual mesh¶

Export:

File -> Export -> Collada (.dae)

Recommended export options:

Apply Modifiers
Selected Objects
Triangulate

Example output:

robot_visual.dae

8) Create and export the collision mesh¶

Duplicate the object:

Shift + D

Rename:

robot_collision

Apply heavier simplification:

Decimate Ratio = 0.05

Export:

File -> Export -> STL

Example output:

robot_collision.stl

Expected result:

collision mesh is much lower poly than visual mesh
collision checks run faster in simulation

URDF Integration¶

Use separate visual and collision references:

<link name="base_link">

  <visual>
    <geometry>
      <mesh filename="package://robot_description/meshes/robot_visual.dae"/>
    </geometry>
  </visual>

  <collision>
    <geometry>
      <mesh filename="package://robot_description/meshes/robot_collision.stl"/>
    </geometry>
  </collision>

</link>

Mesh Budgets¶

Mesh Type	Recommended Faces
Visual	`< 50k`
Collision	`< 5k`

Troubleshooting¶

Symptom	Likely cause	Fix
Missing faces in Gazebo	flipped normals	recalculate normals and check face orientation
Wrong robot size in simulation	unapplied scale	apply `Rotation & Scale` before export
Slow simulation	collision mesh too detailed	lower collision decimate ratio
Unstable collisions	tiny CAD details in collision mesh	remove screws/threads/fillets from collision mesh
Mesh looks broken after export	duplicate vertices / bad topology	rerun `By Distance`, then triangulate

Best Practices¶

Remove decorative CAD details that do not affect physics.
Keep collision geometry simple and convex where possible.
Keep mesh names and file names explicit (*_visual, *_collision).
Test meshes in RViz and Gazebo before integrating into a full stack.

Next Steps¶

validate TF and inertia after mesh import in URDF
test with your robot controllers in Gazebo
tune collision quality only as much as needed for reliable contact

This workflow helps meshes render correctly, load faster, and simulate more reliably in ROS 2 projects.