Mechanical Visual Truth

Project-independent mechanical CAD, STEP verification, proof rendering and MCP tools.

One declarative YAML contract drives real CadQuery/Open CASCADE solids, STEP export, native technical drawings, VTK proof renders, sampled animation and audits. Use the command line, Python API, or a local stdio MCP client.

Explore the drawings, renders, STEP downloads and motion proof →

Install

Python 3.12 is the supported runtime. A fresh virtual environment is recommended.

git clone https://github.com/ufukefekaya-tr/mechanical-visual-truth.git
cd mechanical-visual-truth
python3.12 -m venv .venv
.venv/bin/python -m pip install -e '.[dev]'
.venv/bin/mvt doctor

VTK uses offscreen rendering. On Linux, install the platform's OpenGL/EGL runtime; an Xvfb session is another option on hosts without a suitable driver. No cloud account or model API key is required.

Related MCP server: AgentCAD

Start any project

mvt project init ./my-assembly --template fixture-stage
mvt contract validate ./my-assembly
mvt build ./my-assembly
mvt render ./my-assembly --set proofs
mvt audit ./my-assembly
mvt animate build ./my-assembly --sequence shuttle

Available templates: fixture-stage, linear-actuator, instrument-enclosure. They are original synthetic examples, with no customer models or vendor CAD. Paths are explicit; projects can live outside this source checkout.

Edit the contract to define entities, dimensions, materials, cameras and audit requirements. Primitive geometry and hash-locked local STEP/BREP sources can share one entity registry. A source belongs to its contract directory; it is never discovered through another project, a global library or a server path.

# Preview geometry before producing a STEP deliverable:
mvt build ./my-assembly --no-step

# Inspect any STEP, or create a true vector projection drawing:
mvt step inspect ./part.step --json
mvt step drawing ./part.step ./part-drawing.svg --title 'Example part'

The drawing contains orthographic projections and overall dimensions in mm. It is not a GD&T, tolerance, material or manufacturing approval package.

MCP

Start a workspace-scoped server with the official Python MCP SDK:

mvt-mcp --workspace /absolute/path/to/workspace

Example MCP host configuration (replace the two paths):

{
  "mcpServers": {
    "mechanical-visual-truth": {
      "command": "/absolute/path/to/.venv/bin/mvt-mcp",
      "args": ["--workspace", "/absolute/path/to/workspace"]
    }
  }
}

The tools create/read/update contracts, validate, build, render, audit, animate, inspect STEP, draw SVG and list artifacts. Inputs use workspace-relative paths. CAD workers are serialized and time bounded. Existing contract updates require their current hash. There is no shell, arbitrary-code, publish or automatic acceptance tool. See MCP tools and boundaries.

What an audit proves

• Actual B-rep geometry, declared counts, placements, envelope and constraints.

• Independent STEP reload with solid inventory, validity, volume, bounds and geometry comparisons.

• Contract/model/source hashes connecting geometry, images and generated runs.

• Sampled motion checks only for the actors, pairs and times explicitly declared.

Concept visualization, geometric verification and physical/safety qualification are separate. A geometry PASS does not certify a mechanism, motor, load capacity, manufacturing drawing or safe machine. Presentation-only imagery never becomes the geometric master. Missing or deferred checks remain visible.

Reproduce and extend

pytest
python scripts/generate_gallery.py
python -m build

The gallery generator uses temporary copies of the bundled contracts and records artifact hashes. Development lessons recovered from later STEP-producing tools are described in Upstreamed improvements. Customer parts, private project state and old Git history are excluded from this public tree.

Optional workspace governance includes a local index, acceptance ledger, compact handoffs and reversible rules. It is not required for CAD or MCP use. See operations, animation, and the repository skills.

License and authorship

Copyright 2026 Ufuk Efe Kaya.

Original source, documentation, synthetic example geometry and generated example media are dual licensed under MIT OR Apache-2.0, at your option. See LICENSE, LICENSE-MIT, LICENSE-APACHE and NOTICE. Dependencies retain their own licenses.