Add missing opencamlib for blender

programs/art.nix

@@ -1,6 +1,41 @@
 { lib, config, pkgs, ... }: let
   py3 = pkgs.python3;
   py3Pkgs = py3.pkgs;
+  # For 3D CNC machining
+  opencamlib = py3Pkgs.toPythonModule (pkgs.stdenv.mkDerivation rec {
+    pname = "opencamlib";
+    version = "2019.07";
+    nativeBuildInputs = (with pkgs;[
+      cmake
+      git
+      doxygen
+      boost
+      texlive.combined.scheme-full
+    ]);
+    propagatedNativeBuildInputs = (with pkgs; [
+      py3
+      py3.pkgs.boost
+      py3.pkgs.vtk
+    ]);
+    postPatch = ''
+        mkdir -p $out/${py3.sitePackages}/{lib,ocl}
+        sed -e 's#LIBRARY DESTINATION ''${PYTHON_ARCH_PACKAGES}#LIBRARY DESTINATION '"$out"'/${py3.sitePackages}#g' -i src/pythonlib/pythonlib.cmake
+        sed -e 's#DESTINATION ''${PYTHON_SITE_PACKAGES}#DESTINATION '"$out"'/${py3.sitePackages}#g' -i src/pythonlib/pythonlib.cmake
+      '';
+    cmakeFlags = [
+      "-DVERSION_STRING=2019.07"
+      "-DBUILD_CXX_LIB=ON"
+      "-DBUILD_PY_LIB=ON"
+      "-DUSE_PY_3=ON"
+      "-DCMAKE_BUILD_TYPE=Release"
+    ];
+    src = pkgs.fetchFromGitHub {
+      owner = "aewallin";
+      repo = "opencamlib";
+      rev = "2019.07";
+      sha256 = "1a8pxp1mh8x3bfsb0l97vgxrpk482p7q9jprkd4m9hv69vva2bdz";
+    };
+  });
   equation = py3Pkgs.buildPythonPackage {
     pname = "Equation";
     version = "1.2.01";