Applying Constraints to X-Topology Curve Control Points

Next the tutorial looks at the effect of apply constraints to individual control points.

6. Remove the cubic spline curve constraint and return the control points of the curve to the original arrangement.

7. A knuckle or cusp in the curve can be created using the knuckle point constraint. Select a point on the curve...

...and from the Right-Click menu, choose Knuckle Point, (Right-Click -> X-Topology Curve -> Knuckle Point).

The curve now interpolates the control point and forms a sharp corner. The curve is now constructed from two separate BSpline curves separated by the control point that has had the knuckle point applied.

8. A straight section in the curve can be created by applying the Straight segment constraint. Select two contiguous points on the curve...

...and from the Right-Click menu, choose Straight segment, (Right-Click -> X-Topology Curve -> Straight Segment).

A Straight section is now formed in the curve. At this point the curve is now based on four different segments. Straight segments can be created by selecting more that two contiguous points. In this case, the internal points of the straight segment will be removed from the curve definition.

9. The Interpolate Point constraint forces the curve to interpolate individual points. Select a number of contiguous points on the curve...

...and from the Right-Click menu, choose Interpolate Point, (Right-Click -> X-Topology Curve -> Interpolate Point).

Part of the curve will now behave as a cubic spline, interpolating the specified control points. If all of the internal control points have the Interpolate Point constraint to them (and there are no other constraint) then the curve will behave in exactly the same manner as if the Cubic Spline Curve constaint had been applied to the whole curve. The 'Cubic Spline Knot Vector based on Chord Length' applies to the Interpolate Point constraint in the same way as it does to the Cubic Spline Curve constraint.

There is also a Blended segment constraint which can be used to join two segements of curve together with tangent continuity (C1).

10. Remove all the existing constraints from the curve. Knuckle and Interpolations constraints can be removed by selecting the points and using the Right-Click menu. To remove the Straight segment constraint, select both end points of the section of curve.

11. Select two contiguous control points...

...and from the Right-Click menu, choose Blended segment, (Right-Click -> X-Topology Curve -> Blended Segment).

A section of curve is formed which interpolates the two control points and is tangential to the two adjacent sections of the curve.

Referencing Other Curve Geometry >>>