message: clarify requirements
diff: @@ -149,7 +149,12 @@ public:
  * Generates a prefiltered cubemap.
  * @param options Options for this environment
  * @param environmentCubemap Environment cubemap (input). Can't be null.
  - * @param outReflectionsTexture Output prefiltered texture or if null it is created.
  + * This cubemap must be SAMPLEABLE.
  + * @param outReflectionsTexture Output prefiltered texture or, if null, it is
  + * automatically created. outReflectionsTexture must
  + * be a cubemap, it must have at least COLOR_ATTACHMENT and
  + * SAMPLEABLE usages and at least the same number of levels
  + * than requested by Config.
  * @return returns outReflectionsTexture
  */
  filament::Texture* operator()(Options options,
  @@ -157,7 +162,7 @@ public:
  filament::Texture* outReflectionsTexture = nullptr);
  /**
  - * Generates a prefiltered cubemap with the default options
  + * Generates a prefiltered cubemap with the default options.
  * @param environmentCubemap
  * @param outReflectionsTexture
  * @return
  