This video defines star points and T points and shows a few methods to control these points.
It is important to be aware of the location of star points and T points in a T-Spline body. Star points and T points affect your ability to easily edit bodies.
T-Splines can have partial rows of control points. These terminate in T points, hence the name T-Splines. T points can be created by many commands, such as insert edge, insert point, subdivide face, merging, and welding, and are used to constrain detail to part of the surface. The surface around a T point will stay smooth, and will not stretch or kink. Mathematically speaking, T points are curvature continuous (C2).
Star points allow a T-Spline to be non-rectangular. Star points can be generated by commands such as extrude, delete face, and merge. It is more difficult to control the shape of a T-Spline at star points, so they should only be used where necessary. Place star points on flatter parts of the surface to more predictably obtain an aesthetically pleasing model. Poor locations for star point placement include sharper parts of the model like creased edges, parts where the curvature changes significantly, or on the edge of an open surface.
Star points also determine how a T-Spline will be converted to BREP. When a T-Spline is converted to BREP, it will split into separate surfaces at each star point.
Length: 2:12