Time update geometry update dependency.

Auto

Default option to work with. In most cases geometry rebuilds on frame update.

Local

Enforces to rebuild geometry at each frame update.

Global

Restrict to rebuild geometry only in case of frame update.

If object is provided here then it and all its subtree would be used as the source of splines instead of generator's own children sub-tree.

Enabled — Source object would be hidden from both render and viewport.
Due to Cinema4D specific issues, this approach is worse than just hide object by deactivating source object's native Viewport Visibility and Render Visibility.

Geometry's generating space

Local

Geometry is generating in local space of the generator, so it would depend to Outliner object transform.

Global

Geometry is generating in world space, so it would be independent of Outliner object transform.

Handle source spline(s) controls points.

Knots

Original spline knots are taken as the source.
Same as having or making spline editable with the least points and point-tangents.
Source spline deformations are missed in that case.

Points

Final source representation (linear spline for spline object) is taken as the source.
Same as applying Current State to Object to the source geometry.
In some cases this method doesn't give proper shape if dynamics is applied to the source geometry.

Cache

Final source representation (linear spline for spline object) is taken as the source.
This method is faster than Points and allows to get final representation of the source geometry with applied dynamics transformations.
Usually it's required to drop source into Object field and put generator lower than the source object in the Object Manager because of Cinema4D's internal calculation order.

Offset distance

Disabled — original geometry is removed, new geometry is rendered.
Enabled — both original and offset geometry are rendered.

Attempts to prevent rail over-twisting along original guide.

Off

No control over twisting. Stable during playback, but in some areas there might be 180° twists.

No Flip

Once algorithm detects twist more than 90° it flips rail along guide.

Limit

Limiting twisting angle.

Maximum twist angle

Applies to closed splines only. Smooths rail ending to it's begining, there would be no over-twist.

Enables Smooth Closure algorithm.

Maximum twist (normal vector) angle relatively to previous rail geometry.

Enables Torsion solver.

Creates blend between current and previous rail geometry (normal vector blend).

Enables Stiffness solver.

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.

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).

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.

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.

Fields falloff to control Outliner's offset.