🪟 Windows Native

The solver runs directly as a Windows subprocess using a bundled Python interpreter and (optionally) a bundled CUDA runtime. No SSH or Docker is involved – the add-on launches the solver alongside Blender and talks to it over a local TCP socket.

Block diagram with a single Blender workstation (Windows) box that contains the add-on on the left and server.py running under python.exe on the right. A blue solid arrow labelled CreateProcess (no console window) points from the add-on to server.py; a purple dashed arrow labelled socket to localhost:9090 carries server traffic between them.

Where each piece lives, and how the add-on reaches it. The add-on launches server.py as a hidden subprocess via CreateProcess (blue solid arrow) and then talks to it over a loopback TCP socket (purple dashed arrow). Everything stays on the same Windows machine – no SSH and no Docker.

Note

Unlike the Local (Linux) backend, the Windows Native build ships as a self-contained tree: the embedded Python interpreter, CUDA runtime, Rust solver binaries, and all third-party shared libraries live entirely under the install root. Nothing is installed into the system, no apt packages, no shell rc edits, no global services. Uninstalling is just deleting the bundled directory; there is no contamination of the host to clean up.

When to Use It

  • User workstations running Blender on Windows with a local NVIDIA GPU.

  • Bundled deployments that ship the solver next to the add-on.

  • Reproducible test rigs where you want the exact shipped Python + CUDA, not whatever the system has.

Setup

  1. Set Server Type to Windows Native.

  2. Set Solver Path to the root of your solver install. This is the directory that contains server.py plus either a shipped python\ subfolder (redistributable bundle) or a build-win-native\python\ subfolder (developer build).

  3. Click Connect. The add-on verifies server.py is where it should be, picks up the right Python runtime, and launches the solver as a hidden subprocess on port 9090.

  4. The server is launched as part of the connect step, so once Connect reports success the server is already running. Pressing Start Server afterwards is a no-op on this backend.

Backend Communicator panel in Windows Native mode

Backend Communicator with Server Type set to Windows Native. Only Solver Path and Project Name appear, with no SSH or Docker fields. Connect is highlighted.

Fields

Field

Description

Solver Path

Root directory containing server.py plus either python\ (bundle) or build-win-native\python\ (dev).

Troubleshooting

  • server.py not found: <root>\server.py - the root points at the wrong directory. It must be the solver checkout root, not the python\ subdirectory.

  • Embedded Python not found ... - the add-on could not find a Python runtime under the root. Either rebuild the dev tree, or download and unpack the bundle zip.

  • CUDA DLL load errors - on the shipped bundle, the solver relies on the system CUDA runtime. Install a matching CUDA version, or switch to the developer build which ships its own CUDA.

Under the hood

Layout auto-detection

Connect picks one of two layouts by looking for python.exe:

Dev layout

<root>/
  server.py
  build-win-native/
    python/python.exe
    cuda/bin/*.dll
  target/release/          # Rust solver binaries
  src/cpp/build/lib/

Used when you built the solver from source. The Python interpreter is build-win-native\python\python.exe, CUDA_PATH is set to build-win-native\cuda, and the launcher prepends, in order, build-win-native\python, target\release, src\cpp\build\lib, and build-win-native\cuda\bin to PATH.

Bundle layout

<root>/
  server.py
  python/python.exe
  bin/                     # native shared libraries
  target/release/

Used by a shipped redistributable. The Python interpreter is root\python\python.exe, CUDA_PATH is not set (CUDA is expected on the system PATH), and the launcher prepends root\python, root\bin, and root\target\release.

If neither interpreter is present, connect fails with:

Embedded Python not found in <build_dir> or <root>

Subprocess environment

The subprocess inherits your current environment with a few additions:

  • PATH is prepended with the layout-specific directories above; the existing PATH is appended so system tools still work.

  • PYTHONPATH begins with <root> so server.py can import its own modules.

  • CUDA_PATH is added on the dev layout only.

Launch flags

The solver is launched as python.exe server.py --port <port> with no visible console window, so nothing appears behind Blender.

Shutdown

On disconnect (or Stop Server), the add-on asks the subprocess to terminate and waits up to 5 seconds; if it is still alive, it is killed. The Unix pkill -f server.py path is not used; the backend holds the Windows process handle directly.

Why Start Server is a no-op

The subprocess is started as part of the Connect step, so by the time Connect reports success the server is already running. Pressing Start Server afterwards has nothing to do.