message: Ptex links with libz under Linux
  ..and presumable under Win32, too
diff: @@ -24,6 +24,7 @@ find_package(GLUT REQUIRED)
  find_package(OpenGL REQUIRED)
  find_package(Ptex)
  find_package(Threads REQUIRED)
  +find_package(ZLIB) # Ptex links with libz
  visionaray_use_package(Boost)
  visionaray_use_package(GLEW)
  @@ -31,6 +32,7 @@ visionaray_use_package(GLUT)
  visionaray_use_package(OpenGL)
  visionaray_use_package(Ptex)
  visionaray_use_package(Threads)
  +visionaray_use_package(ZLIB)
  # CUDA
  