Mastering JBeam: A Beginner’s Guide to BeamNG.drive Modding

Mastering JBeam: A Beginner’s Guide to BeamNG.drive Modding

What is JBeam?

JBeam is the text-based physics definition format used by BeamNG.drive to describe vehicle and object structures: nodes (points), beams (connections), collision shapes, and physical properties. It tells the engine how parts deform, break, and interact.

Tools you’ll need

• BeamNG.drive (installed)
• A text editor (VS Code, Notepad++, Sublime)
• 3D modeling tool (Blender or similar) — optional for custom meshes
• A file archiver (7-Zip) for packaging mods
• BeamNG’s built-in in-game vehicle editor and JBeam reference files

JBeam file structure (core sections)

• nodes: list of points with coordinates and properties
• beams: connections between nodes defining stiffness and behavior
• flexbodies: mesh-to-node bindings for visual deformation
• materials: physical parameters (mass, stiffness, damping)
• slots: attach points for other parts or mods
• shapes/collision: simplified collision geometry for performance

Basic example

json
Copy CodeCopied
{
“my_vehicle”: {
    “information”: {“authors”: “You”, “name”: “My Vehicle”},
    “nodes”: [
      [“id”, “posX”, “posY”, “posZ”, “mass”]
    ],
    “beams”: [
      [“nodeA”, “nodeB”, “material”, “flags”]
    ],
    “materials”: [
      [“materialName”, “youngsModulus”, “yieldStrength”]
    ]
  }
}

Create a file named vehicle.jbeam inside your mod folder: / vehicles/your_vehicle/vehicle.jbeam

Step-by-step: Create a simple deformable bumper

1. Copy an existing vehicle mod folder as a template.
2. Open its .jbeam file and locate the bumper section.
3. Define nodes for bumper anchor points and outer skin.
4. Connect nodes with beams; set higher stiffness for anchors.
5. Add a flexbody mapping the visual mesh to nodes.
6. Test in-game, tweak beam strengths and damping until deformation looks right.

Key parameters to tweak

• Young’s Modulus (stiffness) — higher = less deformation
• Yield Strength — determines when beams break
• Damping — controls oscillation after impact
• Beam flags — define behavior like shear, compression, and break patterns

Debugging tips

• Use in-game JBeam validator (console) to catch syntax errors.
• Start with small changes; test frequently.
• Visualize nodes/beams in editor to ensure correct alignment with mesh.
• If collision is off, simplify collision shapes first.

Best practices

• Use relative coordinates centered on a logical pivot (e.g., vehicle origin).
• Name nodes and materials clearly.
• Keep beams organized by function (frame, suspension, skin).
• Balance realism and performance: more nodes = better deformation