anchor.diff:  { config, stdenv, lib, fetchurl, fetchzip, boost, cmake, ffmpeg, gettext, glew
   , ilmbase, libXi, libX11, libXext, libXrender
   , libjpeg, libpng, libsamplerate, libsndfile
  -, libtiff, libGLU, libGL, openal, opencolorio, openexr, openimagedenoise, openimageio2, openjpeg, python3Packages
  +, libtiff, libGLU, libGL, openal, opencolorio, openexr, openimagedenoise, openimageio2, openjpeg, python39Packages
   , openvdb, libXxf86vm, tbb, alembic
   , zlib, fftw, opensubdiv, freetype, jemalloc, ocl-icd, addOpenGLRunpath
   , jackaudioSupport ? false, libjack2
  
positive.code: 
  with lib;
  let
    python = python3Packages.python;
    optix = fetchzip {
      url = "https://developer.download.nvidia.com/redist/optix/v7.0/OptiX-7.0.0-include.zip";
      sha256 = "1b3ccd3197anya2bj3psxdrvrpfgiwva5zfv2xmyrl73nb2dvfr7";
  
negative.code:       "-DPYTHON_VERSION=${python.pythonVersion}"
        "-DWITH_PYTHON_INSTALL=OFF"
        "-DWITH_PYTHON_INSTALL_NUMPY=OFF"
        "-DPYTHON_NUMPY_PATH=${python39Packages.numpy}/${python.sitePackages}"
        "-DPYTHON_NUMPY_INCLUDE_DIRS=${python39Packages.numpy}/${python.sitePackages}/numpy/core/include"
        "-DWITH_PYTHON_INSTALL_REQUESTS=OFF"
        "-DWITH_OPENVDB=ON"
        "-DWITH_TBB=ON"
  