Teacup β-B-spline surface editor The 4×4 rectangles are rendered as β-modified bicubic B-spline patches. β = 0 gives the ordinary clamped cubic B-spline with U = V = [0,0,0,0,1,1,1,1]. Drag a red control point to deform the surface. Hold Shift while dragging to move along view depth. Drag empty space to orbit. Mouse wheel zooms.