As a sit start from the tufa like feature that his feet are on, you can do one of two things. Staying on the right side of the arete and utilizing the crimp shared by the Cube Problem, you can go straight up, this is Rain Dance. If you use the arete and the face to the left, you are doing a problem that is, in my opinion, slightly different than Barb Wire, which I believe starts on the face standing and uses good holds. I have always called this "in between" problem Pole Dancer.
You ask about starting on the undercling. If you mean the undercling to the right of the person in the picture, then you are refering to the stand start of the Cube.
Of course, you can climb into any climb from any start on this boulder. Welcome to the land of bored climbers and their many contrivances.