Model Viewer - 3D Model Inspection

View and inspect OpenSCAD (.scad) and STL (.stl) 3D models using the openscad-viewer: MCP tools.

Prerequisites

• OpenSCAD must be installed and on $PATH (for .scad files; not needed for .stl)
• The openscad-viewer MCP server must be running

Starting the Viewer Manually

If the MCP server is not already connected, start it manually:

npx openscad-viewer <file.scad|file.stl>

This opens a browser window at http://localhost:8439 showing the 3D model. The user sees the same view the agent is inspecting.

MCP Tools

openscad-viewer:open

Opens a .scad or .stl file in the viewer. Use this to load or switch models.

Parameters:

• file (required): Absolute or relative path to a .scad or .stl file

Returns:

{
  "success": true,
  "file": "/absolute/path/to/model.scad",
  "fileSize": 2048,
  "boundingBox": { "min": [-10, -10, 0], "max": [10, 10, 20] }
}

The bounding box tells you the model's dimensions. Use it to:

• Understand the scale of the model
• Calculate appropriate camera distance
• Verify geometry changes after edits

openscad-viewer:view

Renders the current model at a specified camera angle and returns a PNG screenshot.

Parameters:

• azimuth (optional, default 45): Horizontal angle 0-360 degrees
• elevation (optional, default 30): Vertical angle -90 to 90 degrees
• distance (optional): Distance from model center. Auto-calculated from bounding box if omitted.

Returns:

{
  "imagePath": "/tmp/openscad-viewer-capture-xxxxx.png",
  "camera": { "azimuth": 45, "elevation": 30, "distance": 100 }
}

Read the returned imagePath to see the rendered model.

Side effect: The browser view animates to the requested angle, so the user sees what you are looking at.

Standard Views Quick Reference

Inspection Workflow

When inspecting or verifying a model:

1. Front view: view { "azimuth": 0, "elevation": 0 }
2. Top view: view { "azimuth": 0, "elevation": 90 }
3. Isometric view: view { "azimuth": 45, "elevation": 30 } (default)
4. Right side: view { "azimuth": 90, "elevation": 0 }

Edit-View Cycle

When modifying OpenSCAD code:

1. Edit the .scad file
2. The viewer auto-recompiles and updates (file watching is built in)
3. Use view to verify the change from relevant angles
4. If there is a compilation error, the viewer keeps the last good model visible and shows the error
5. Fix the error and save again — the viewer updates automatically

Tips

• You do not need to call open after editing a file — the viewer watches for changes automatically
• Call open only when switching to a different file
• The bounding box from open helps estimate appropriate camera distances
• Use elevation 90 (top-down) to check X/Y layout, elevation 0 for Z height
• Auto-distance works well for most models — only set distance manually for close-up details