DEV Community: Ravindhar

Convert URDF to MuJoCo MJCF Without Installing Anything

Ravindhar — Wed, 06 May 2026 20:03:06 +0000

If you've tried converting URDF to MuJoCo MJCF, you know the pain:

MuJoCo's ./compile deletes fixed base links
urdf2mjcf ignores off-diagonal inertia terms
Mesh paths break constantly
No automatic actuator generation

I built an API that handles all of this in one HTTP call.

One curl command

curl -X POST https://roboinfra-api.azurewebsites.net/api/urdf/convert-format?target=mjcf \
  -H "X-Api-Key: rk_your_key" \
  -F "file=@robot.urdf"

Real example

Input URDF (6 links, 5 joints):

Output MJCF:

Notice what the API auto-generated:

Nested body tree (respects URDF kinematic chain)
4 motor actuators for movable joints (skipped fixed joint)
Floor plane, lighting, compiler settings
Half-extent box conversion (URDF 0.15 → MJCF 0.075)
Continuous joint correctly mapped to unlimited hinge

Python SDK

pip install roboinfra-sdk

import roboinfra
client = roboinfra.Client("rk_your_key")
result = client.urdf.convert_format("robot.urdf", "mjcf")
with open("robot.xml", "w") as f:
    f.write(result.converted_xml)

Also converts to Gazebo SDF

Just change target=sdf:

curl -X POST .../api/urdf/convert-format?target=sdf \
  -H "X-Api-Key: rk_..." -F "file=@robot.urdf"

Free 14-day Pro trial

No credit card. Sign up: https://roboinfra-dashboard.azurewebsites.net

Convert URDF to MuJoCo MJCF Without Installing Anything

Ravindhar — Tue, 05 May 2026 18:47:00 +0000

I validated and converted URDFs from 5 popular robots to both
Gazebo SDF and MuJoCo MJCF format. Here's what I found:

The tool is free to try (14-day Pro trial, no credit card):

https://roboinfra-dashboard.azurewebsites.net/validator

Validate: POST /api/urdf/validate
Convert to SDF: POST /api/urdf/convert-format?target=sdf
Convert to MJCF: POST /api/urdf/convert-format?target=mjcf

Python SDK: pip install roboinfra-sdk
GitHub Action: roboinfra/validate-urdf-action@v1

How to Validate URDF Files in GitHub Actions Without Installing ROS

Ravindhar — Sun, 03 May 2026 11:37:09 +0000

The problem (3 sentences)
- ROS CI pipelines are slow because check_urdf needs full ROS install
- Most GitHub Actions runners don't have ROS
- You just want to catch broken joint refs before merging
The solution (show the YAML)
- 6 lines of GitHub Action config
- No ROS install, no Docker, runs in 5 seconds
Real example (screenshot)
- Show NASA Robonaut 2 URDF passing validation
- Show a broken URDF failing with clear error messages
How to set it up (step by step)
- Create free account (link)
- Copy API key to GitHub Secrets
- Add the YAML to your repo
Free tier: 50 validations/month, no credit card

Convert URDF to MuJoCo MJCF Without Installing Anything API + Python SDK

Ravindhar — Sun, 03 May 2026 11:22:24 +0000

The Problem (3 paragraphs)
- MuJoCo is the fastest-growing robotics simulator
- Converting URDF to MJCF is painful (./compile is buggy, urdf2mjcf ignores off-diagonal inertia, mesh paths break)
- You just want to convert and start training your RL agent
The Solution (show curl + Python code)
curl -X POST .../api/urdf/convert-format?target=mjcf \
-H "X-Api-Key: rk_..." -F "file=@robot.urdf"

import roboinfra
client = roboinfra.Client("rk_...")
result = client.urdf.convert_format("robot.urdf", "mjcf")
with open("robot.xml", "w") as f:
f.write(result.converted_xml)

Real Example (use your preview_test_arm.urdf)
- Show the input URDF (6 links, 5 joints)
- Show the output MJCF (with actuators, floor, lighting)
- "This would take 2-3 hours manually. API did it in 200ms."
Also Converts to Gazebo SDF
- Same API, just change target=sdf
- Show the SDF output
Bonus: Validate + Convert in CI
- GitHub Action YAML (6 lines)
- Validate URDF + convert to MJCF on every push
Free 14-day Pro trial, no credit card
Link: https://roboinfra-dashboard.azurewebsites.net

How to Validate URDF Files in GitHub Actions Without Installing ROS

Ravindhar — Sun, 03 May 2026 11:21:00 +0000

The Problem (3 paragraphs)
- MuJoCo is the fastest-growing robotics simulator
- Converting URDF to MJCF is painful (./compile is buggy, urdf2mjcf ignores off-diagonal inertia, mesh paths break)
- You just want to convert and start training your RL agent
The Solution (show curl + Python code)
curl -X POST .../api/urdf/convert-format?target=mjcf \
-H "X-Api-Key: rk_..." -F "file=@robot.urdf"

import roboinfra
client = roboinfra.Client("rk_...")
result = client.urdf.convert_format("robot.urdf", "mjcf")
with open("robot.xml", "w") as f:
f.write(result.converted_xml)

Real Example (use your preview_test_arm.urdf)
- Show the input URDF (6 links, 5 joints)
- Show the output MJCF (with actuators, floor, lighting)
- "This would take 2-3 hours manually. API did it in 200ms."
Also Converts to Gazebo SDF
- Same API, just change target=sdf
- Show the SDF output
Bonus: Validate + Convert in CI
- GitHub Action YAML (6 lines)
- Validate URDF + convert to MJCF on every push
Free 14-day Pro trial, no credit card
Link: https://roboinfra-dashboard.azurewebsites.net

How to validate URDF files in GitHub Actions without installing ROS

Ravindhar — Tue, 21 Apr 2026 18:59:27 +0000

The problem: ROS CI pipelines are slow because check_urdf
needs a full ROS install (1GB+)
The solution: a 3-line GitHub Action that validates URDFs
via API (show your Action YAML)
Real example: I ran NASA Robonaut 2's URDF through it
and found... (show the results)
How to set it up (step by step with screenshots)
Free tier: 50 validations/month, no credit card

built a free validator:

https://roboinfra-dashboard.azurewebsites.net/validator
(no signup, runs in browser)

🔒
Your files are safe

Never stored: file contents exist only in memory during the request. Not written to disk, database, or logs.

Never used for training: We do not use uploads to train AI models or for any purpose beyond your requested validation.

Never shared: We do not share uploaded files with third parties.

Metadata logged 30 days: File size in bytes, validation result (valid/invalid), error count, and timestamp. Used for abuse prevention only.

After response: file content is garbage-collected and unrecoverable.