anchor.diff:       sha256 = "0w3argjy1biaxwa3c80zxxgll67wjp8czd83p87awlcvwzdk5mz9";
     };
   
  -  cmakeFlags = [ "-DOGRE_INSTALL_SAMPLES=yes" ]
  -    ++ (map (x: "-DOGRE_BUILD_PLUGIN_${x}=on")
  -            [ "BSP" "CG" "OCTREE" "PCZ" "PFX" ])
  -    ++ (map (x: "-DOGRE_BUILD_RENDERSYSTEM_${x}=on") [ "GL" ]);
  +  cmakeFlags = [ "-DOGRE_BUILD_SAMPLES=${toString withSamples}" ]
  +    ++ map (x: "-DOGRE_BUILD_PLUGIN_${x}=on")
  +           ([ "BSP" "OCTREE" "PCZ" "PFX" ] ++ lib.optional withNvidiaCg "CG")
  +    ++ map (x: "-DOGRE_BUILD_RENDERSYSTEM_${x}=on") [ "GL" ];
   
     enableParallelBuilding = true;
   
  
positive.code: { fetchurl, stdenv
  , cmake, mesa
  , freetype, freeimage, zziplib, randrproto, libXrandr
  , libXaw, freeglut, libXt, libpng, boost, ois
  , xproto, libX11, libXmu, libSM, pkgconfig
  , libXxf86vm, xf86vidmodeproto, libICE
  , renderproto, libXrender
  , nvidia_cg_toolkit }:
  
  stdenv.mkDerivation {
    name = "ogre-1.9-hg-20160322";
  
negative.code:      xproto libX11 libXmu libSM pkgconfig
       libXxf86vm xf86vidmodeproto libICE
       renderproto libXrender
     ] ++ lib.optional withNvidiaCg nvidia_cg_toolkit;
  
    meta = {
      description = "A 3D engine";
  