anchor.diff: -{stdenv, fetchurl, qt4, bzip2, lib3ds, levmar, muparser, unzip}:
  +{ stdenv, fetchurl, qt4, bzip2, lib3ds, levmar, muparser, unzip, vcg }:
   
   stdenv.mkDerivation rec {
     name = "meshlab-1.3.3";
  
positive.code: 
    sourceRoot = ".";
  
    buildInputs = [ qt4 unzip ];
  
    meta = {
      description = "System for the processing and editing of unstructured 3D triangular meshes";
  
negative.code: 
    buildPhase = ''
      mkdir -p "$out/include"
      export NIX_LDFLAGS="-rpath $out/opt/meshlab $NIX_LDFLAGS"
      cd meshlab/src
      pushd external
  