Beyonce's younger sister popped up in Houston Saturday with a whole film crew behind her ... and a camera in hand. Eyewitnesses tell us she made an appearance at the SHAPE Community Center off of Almeda Rd. and Alabama St., where we're told she was chatting up folks inside and discussing different shots she wanted to get.

One eyewitness told us it appeared she was at the helm of either a movie or documentary of some sort ... and was trying to keep it low key.

Solange hasn't announced any new film projects as of late, and nothing official seems to be in production under her IMDb page either. That doesn't mean something isn't in the works though. And besides, she's already got a couple visual projects under her belt.

She put out a behind-the-scenes documentary about the making of her 2016 album, "A Seat at the Table," and also directed SZA's 2017 music video for "The Weekend."

While she hasn't put out much new music since her Grammy-winning record, she has been busy heading up art pieces in L.A. ... and teasing us with a follow-up album that has yet to be released.