Type
Linear
This simplest of all the spline types connects the vertices, which define the polygon, with straight, directly connected lines. You can use these splines to create angular objects or to simulate sharp jerky movements for animation.
Cubic
This kind of spline has a soft curve between vertices. The interpolated curve passes directly through the vertices. Looking at the two points at the top right of the diagram, you can see that the curve bulges more than is probably required. This behavior is called overshooting, and it often appears with closed curvatures. This becomes clearer when you compare this section of the curve with the same section of the curve with Akima interpolation.
Akima
This spline type creates a soft curve between vertices. The interpolated curve always passes directly through the vertices. Overshooting does not happen with this type of curve. Akima interpolation adheres very closely to the path of the curve directly between the vertices but, because of this, it can sometimes appear somewhat hard. If this is not required, you should use Cubic interpolation.
B-Spline
This kind of spline also creates a soft curve between the vertices. However, the curve does not pass directly through the vertices. This produces a very smooth curve. The vertices control only the approximate path of the curve. Distant points have less influence on the curve than those lying closer together.
Bezier
This spline type creates a soft curve path between the vertices, which can be controlled very precisely. The interpolated curve always passes through the vertices. Overshoot does not happen.
Closed
Each spline segment can be closed or open. If a spline is closed, the start and end points are seamless connected.
Open
Makes spline segments open ending.
Close
Makes spline segments closed.
Auto
Makes spline segments open or closed depending of source(s).
Fix Closure
If Closed is set as Open or Auto and there are closed source splines — additional point would be created after the original end point in place of the original start point
So while being open spline, it would look like closed spline.
Interpolation
Here you can define how the spline is further subdivided with intermediate points. This affects the number of subdivisions created when using the spline with Generator objects.
None
This method of interpolation locates points only at the vertices of a spline, using no additional intermediate points. You cannot enter values into the Number or Angle boxes. For B-splines, the vertices, and therefore points, might not be located on the spline curve.
Natural
This interpolation type first locates points at spline vertices. In the case of B-splines, points are located at positions on the spline curve closest to the spline vertices. Number (N) corresponds to the number of intermediate points between vertices. The points are positioned closer together on areas of the spline with more curvature.
You cannot enter values into the Angle box.
Uniform
This interpolation subdivides the spline so that the distance between any two consecutive points, as measured along the spline curvature, is constant. One point is always located at the beginning vertex. For open splines, a point is also located at the ending vertex. Other points generally do not coincide with vertices.<
You cannot enter values into the Angle box.
Adaptive
This interpolation type sets intermediate points whenever the angle deviation of the curve is larger than the value given in Angle. The points of the resulting curve pass through the vertices. If a spline has several segments, then the value of Angle will apply to each segment.
The Adaptive method gives the best results in rendering, hence it is the default interpolation method.
You cannot enter values into the Number box.
Subdivided
Subdivided is similar to Adaptive. Additional intermediate points will be added until the intermediate segments are shorter than the defined Maximum Length, i.e., the point intervals will not necessarily be equal to the maximum length. Lower values will result in higher quality, along with the disadvantages of working with a high number of points - slower refresh times in the editor view, etc.