The SOLIDWORKS software supports two types of splines, B-splines and style splines.
You can use B-splines to create complex curves. You can define and modify them using several controls, including spline points, spline handles, and control polygons. A single B-spline can have multiple through points and spans (the region between through points). You can apply curvature constraints at each endpoint. At each through point, you can weigh the tangency vector and control the tangency direction.
Style splines, based on Bézier curves, are a good option when it is important to have a smooth curve (that is, to assure curvature continuity). You define and control the curves using control vertices. The control vertices form a control polygon, or hull of the curve. There are no through points, so a style spline has only one span between the endpoints. You can inference style splines for tangency or equal curvature. You can constrain the points and dimension the curves' sides. These curves also support mirroring and self-symmetry.
