spektrafilm OFX is a native OpenFX plugin project built from the spektrafilm film-simulation codebase. It is intended for host applications such as DaVinci Resolve or Nuke and provides Metal/Vulkan-accelerated film, print, scan, grain, halation, diffusion, color-management, and LUT-export workflows on macOS and Windows.

This project is an expansion of spektrafilm by Andrea Volpato. The original project provides the research foundation, Python implementation, profile-generation workflow, and much of the film-density modeling direction.

The OFX work in this directory ports and extends that idea into a native plugin for video applications. The main goals are:

1. Stay true to the spectral and density-based character of the original model.
2. Expand upon the controls for photochemical developemnt simulation (e.g. adding push/pull)
3. Make the pipeline usable in professional video and finishing workflows.
4. Keep spacial effects resolution-independant (1080p and 2160p sample the same virtual film negative, just at different densities)
5. Leverage Apple's Metal GPU stack on macOS and Vulkan compute for Windows and Linux workflows.
6. Provide ready to use OFX binaries for non developers.
7. Keep tools in active development and research controls in a separate dev build.

Prebuilt binaries, release information, and product-facing documentation are available at:

https://spektrafilm.114c.de

The public binary packages are intended for users who only want to install the OFX plugin. Building from source is mainly useful for development, verification, custom resources, or local experimental builds.

The OFX plugin adds several workflow and model extensions on top of the base spektrafilm framework. For a general project overview visit Andrea Volpato's page or read the documentation in documentation/.

The plugin includes explicit input and output color-management controls for common camera, scene-linear, scene-log, SDR display, and HDR output paths. The pipeline decodes input into a scene-referred working representation, runs the film and print model, then encodes the selected output format.

The available output formats are:

The Manage group includes a LUT export path for display-referred SDR looks. Exports are rendered through the native Metal color pipeline as .cube LUTs. Spatial and stochastic effects such as grain, halation, diffusion, scanner blur, and similar image-dependent operations are excluded from the exported LUT as they go beyond the scope of LUT capabilites.

The LUTs are designed to easily work for dailies, on-set monitoring, cross-platform editing and many other workflows.

For spatial effects, Film Format defines the shared virtual film gate used by grain, halation, diffusion, DIR, and scanner optics. Crops and enlarger transforms sample smaller regions of that same negative; output resolution only changes sampling density.

The film-development controls include two push/pull approaches:

Print/paper push and pull is separate from film push and pull. Film push/pull acts around negative development. Print push/pull acts around paper development.

The project contains a printer-light system for APD-based print timing comparable to motion picture printers. It uses printer points where one point equals 1/12 stop of light, matching the common lab timing unit.

This feature depends on SMPTE ST 2065-2 Academy Printing Density data. The relevant CSV files are licensed standards material and are not redistributed in this public repository.

Public source builds without those CSV files still build successfully, but the printer-density mode and printer-point controls will be disabled and the build prints a clear notice when the files are missing.

If you have your own licensed copies of the CSV files attached to ST 2065-2, place them here before configuring the build:

Resources/data/standards/smpte_st_2065_2/st2065-2a-2020.csv
Resources/data/standards/smpte_st_2065_2/st2065-2b-2020.csv

Then re-run CMake from a clean build directory. When both files are present, the generated profile counts header enables the Academy Printer Density path and the printer-light controls become available in the relevant plugin flavors.

The native renderer has experimental negative and print bleach-bypass controls available in the spektrafilm dev build. They are an attempt to model retained silver in the film or print path, but this area is not yet backed by enough stock- and/or process-specific measured data.

For that reason, these controls should not be treated as representative lab controls but as a playful first attempt at modeling this process. They are not exposed in the normal public spektrafilm flow and spektrafilm builds.

Important paths in this directory:

The macOS source build expects:

1. macOS.
2. Xcode Command Line Tools or Xcode.
3. Apple's Metal toolchain available through xcrun.
4. CMake 3.24 or newer.
5. Python with the OFX build-time table generation dependencies installed: numpy, scipy, and colour-science.
6. libpng discoverable by CMake for the variant generator target.
7. OpenFX SDK headers (OFX_Release_1.5.1).

The Windows source build expects:

1. Windows 10 or newer.
2. Visual Studio 2022 C++ build tools, Ninja, or another CMake-supported C++17 toolchain.
3. Vulkan SDK with the Vulkan loader, headers, and glslc or glslangValidator.
4. CMake 3.24 or newer.
5. Python with the OFX build-time table generation dependencies installed: numpy, scipy, and colour-science.
6. OpenFX SDK headers (OFX_Release_1.5.1).

The Linux developer source build expects:

1. Linux x86_64.
2. GCC, Clang, Ninja, or another CMake-supported C++17 toolchain.
3. Vulkan loader and development headers plus glslc or glslangValidator from the Vulkan SDK or distribution packages.
4. CMake 3.24 or newer.
5. Python with the OFX build-time table generation dependencies installed: numpy, scipy, and colour-science.
6. OpenFX SDK headers (OFX_Release_1.5.1).

The OFX build prefers the repository virtual environment at ../../.venv/bin/python on Unix-like platforms and ../../.venv/Scripts/python.exe on Windows when it exists. Otherwise CMake falls back to the Python interpreter found by find_package(Python3). CMake checks for the build-time Python packages during configure and prints the matching pip install command if they are missing.

For ease of use, I developed this project from within Andrea's spektrafilm repository root. To follow the below instructions, pull the latest version of spektrafilm and place the contents of this repo at OFX/SpektraFilm.

From the spektrafilm root, create or sync the Python environment first. This project uses the Python package for build-time table generation.

Using uv:

uv sync --extra dev

Or with a manually managed Python 3.13 environment:

python -m pip install -e ".[dev]"

For an OFX-only build environment, the full GUI/image stack is not required:

python -m pip install numpy scipy colour-science

Then build the OFX project:

cd OFX/SpektraFilm
./build_macos.sh

The script configures CMake, builds the plugin targets, and produces local .ofx.bundle outputs. It does not sign with Developer ID, notarize, or write the public macOS installer ZIP.

To create the signed public macOS release ZIP, first create a notarytool keychain profile, then run the release packager with your Developer ID identities:

xcrun notarytool store-credentials spektrafilm-notary

SPEKTRAFILM_DEVELOPER_ID_APP="Developer ID Application: Your Name (TEAMID)" \
SPEKTRAFILM_DEVELOPER_ID_INSTALLER="Developer ID Installer: Your Name (TEAMID)" \
SPEKTRAFILM_NOTARY_PROFILE="spektrafilm-notary" \
./tools/package_macos_release.sh

The output is a single notarized installer package that installs both public macOS plugins into /Library/OFX/Plugins.

On Windows, run the PowerShell build script instead:

cd OFX\SpektraFilm
.\build_windows.ps1

The Windows script builds local Contents\Win64 OFX bundles for development. It does not create the public website ZIP.

To create the public Windows release ZIP, run the release packager:

.\tools\package_windows_release.ps1

The generated zip contains both public Windows .ofx.bundle directories, install.bat, manual, install instructions, and legal notices. The batch script can be inspected before running; it elevates, removes old public spektrafilm bundles, and copies the new bundles into C:\Program Files\Common Files\OFX\Plugins.

On Linux, use the manual CMake flow. The build creates local Contents/Linux-x86-64 OFX bundles for development and emits SpektraVulkanCopyHarness for the same Vulkan smoke coverage. Linux release packaging is not provided in this phase.

For a more explicit build:

cd OFX/SpektraFilm
cmake -S . -B build
cmake --build build --parallel

To install the built OFX bundles into the system OFX plugin directory:

cmake --install build

The default install destinations are:

macOS:   /Library/OFX/Plugins
Windows: C:/Program Files/Common Files/OFX/Plugins
Linux:   /usr/OFX/Plugins

Depending on your system permissions, installation may require elevated rights.

The build defines three OFX bundle targets:

All three are compiled from the same source. Flavor-specific behavior is controlled through compile definitions and parameter visibility rules in src/SpektraFilmPlugin.cpp.

1. The public source tree does not redistribute licensed SMPTE ST 2065-2 CSV files.
2. Official binary distributions may include bundled resources covered by the notices in Legal/.
3. LUT files exported from the plugin are governed by Legal/SPEKTRAFILM_OFX_LUT_LICENSE.txt.
4. The vendored OpenFX SDK carries its own notices under third_party/openfx/.

The plugin is still an active development project. The public flavors prioritize controls that are useful and reasonably defensible in grading workflows. The dev flavor keeps deeper controls available so that modeling decisions can be tested without committing every experiment to the public UI.

Have fun and thank you for creating with spektrafilm!