anchor.diff:    # Work around a bug in the CMake build:
     postInstall = ''
       chmod a+x $out/bin/*
  +    wrapProgram $out/bin/appleseed.studio --set PYTHONHOME ${python}
     '';
   }
   
  
positive.code: { stdenv, fetchFromGitHub, cmake, boost165, pkgconfig, guile,
  eigen, libpng, python, libGLU, qt4, openexr, openimageio,
  opencolorio, xercesc, ilmbase, osl, seexpr
  }:
  
  let boost_static = boost165.override {
  
negative.code: in stdenv.mkDerivation rec {
  
    name = "appleseed-${version}";
    version = "2.0.5-beta";
  
    src = fetchFromGitHub {
      owner  = "appleseedhq";
      repo   = "appleseed";
      rev    = version;
      sha256 = "1sq9s0rzjksdn8ayp1g17gdqhp7fqks8v1ddd3i5rsl96b04fqx5";
    };
    buildInputs = [
      cmake pkgconfig boost_static guile eigen libpng python
      libGLU qt4 openexr openimageio opencolorio xercesc
      osl seexpr makeWrapper
    ];
  
    NIX_CFLAGS_COMPILE = "-I${openexr.dev}/include/OpenEXR -I${ilmbase.dev}/include/OpenEXR -I${openimageio.dev}/include/OpenImageIO -Wno-unused-but-set-variable";
  
    cmakeFlags = [
        "-DUSE_EXTERNAL_XERCES=ON" "-DUSE_EXTERNAL_OCIO=ON" "-DUSE_EXTERNAL_OIIO=ON"
  