Rihanna Getting Back to Her Half-Naked Roots

 On  Friday ... which means Rihanna was strutting around the earth with no clothes on -- only this time she had an actual reason: Barbados' version of Carnival!!!

Here's what you need to know: these are pics of RiRi lookin' hot in a monokini ... grinding her ass on other girls and having an awesome time. She even tweeted, "Woke up in paint and a veil from partying in de street all morning!!!"

The party was to celebrate her native country's harvest of the sugar crops. But who cares. Here she is two years ago at the same festival ... also half-naked.