[Dabhand16]

In the studio at work they have a frame that holds three rolls of different colour BG material at about 8 feet from the floor. Just like a roller blind, the material can be unrolled downwards and run along the floor with the curve forming naturally, but a former can also be used. Hardboard and ribs as already suggested, or a large diameter plastic pipe cut to allow a curve to be formed.

No blending issues, choice of colour and not too expensive.