message: texture_dimensions<T>::value==0 if T not a texture
diff: @@ -29,7 +29,8 @@ namespace visionaray
  // that returns a point sample
  //
  // - texture_dimensions:
  -// value can be either of {1,2,3}
  +// value can be either of {0,1,2,3}, where 0 denotes that type does
  +// not adhere to concept Texture
  //
  //
  //-------------------------------------------------------------------------------------------------
  @@ -73,8 +74,14 @@ struct is_texture : detail::is_texture_impl<T>::type
  // texture_dimensions
  //
  -template <typename T>
  +template <typename T, typename Enable = void>
  struct texture_dimensions
  +{
  + enum { value = 0 };
  +};
  +
  +template <typename T>
  +struct texture_dimensions<T, typename std::enable_if<is_texture<T>::value>::type>
  {
  enum { value = T::dimensions };
  };
  