anchor: Fixture:getFilterData
  Returns the filter data of the fixture.
  
  Categories and masks are encoded as the bits of a 16-bit integer.
  categories, mask, group = Fixture:getFilterData()
  categories number The categories as an integer from 0 to 65535.
  mask number The mask as an integer from 0 to 65535.
  group number The group as an integer from -32768 to 32767.