Path control points and Bezier points
A path has a position and orientation component (or channel), and can additionally also have a component that describes a velocity profile. A path is defined by control points that describe the path as a succession of linked segments. Control points are only visible when the path is selected:
[Two simple identical path objects. The path on the right-hand side is selected (control points become visible)]
The first control point of a path (the start point) is indicated as a sphere, where the remaining of the control points are indicated as cubes. A path can be open or closed. When closed, it becomes cyclic.
[A closed path]
Each control point has attributes that can describe the path in more details around its vicinity: each control point can describe if and how a Bezier curve should be calculated. Following illustrates this property:
[Two identical path objects. The path on the right-hand side is selected (control points become visible)]
By default, Bezier points are always visible (also when the object is not selected) and are displayed as small red-green-blue arrows indicating the x-, y- and z-axis of the Bezier point (which effectively is a point with orientation). The Bezier curve section is described by 3 parameters as can be seen in following figure:
[Parameters describing a Bezier curve section]
The Bezier interpolation factors indicate where the Bezier curve section starts and ends, and the Bezier point count indicates how detailed (or smooth) the curve should be. A Bezier point count of 1 technically disables the Bezier curve interpolation mechanism, but for simplicity, the control point is then referred to as a Bezier point.
The position and orientation of a control point can be manually adjusted in the path edit mode. A Bezier point orientation however cannot be individually adjusted. It is rather automatically calculated. By default, the orientation of the Bezier points will follow the path curvature (if the automatic orientation option is enabled), otherwise they are interpolated with the control points' orientations as illustrated by following figure:
[Two similar path objects, the left one has the automatic orientation enabled]