An X-Topology curve can control the shape of curves that attach to it. The ribbon tangent group, found on the attributes panel of a X-Topology curve, control the tangent of all referencing curves.
33. Following on from the previous section, delete the second curve. Change the view to (X/Y) Waterlines, (Right-Click -> View -> (X/Y) Waterlines).
34. Draw a new X-Topology curve from bottom to top. Attach the third point to the first curve as shown below.
35. Draw two further control points.
36. Apply a planar Location Surface in the X-Axis.
This will straighten up the curve.
37. Rotate the view and modify the second curve into a slight 'S' shape.
39. Finish editing the second curve and select the first.
40. In the attributes panel, change the Ribbon Tangent to 'Y'.
'Y' vectors are displayed all along the first curve and the second curve changed so that its tangent through the curve follows in the 'Y' vector direction. Zooming in closer show the shape of the curve in more detail.
41. Modifiying the Ribbon Tangent to 'Z'...
...changes the vectors to that the point up and down. The shape of the second curve changes to follow suite.
42. Remove the surface condition by setting thr Ribbon Tangent to 'No Constraint'. Edit the second curve so that it forms a 'U' shape.
43. Finish editing the second curve and select the first. Change the Ribbon tangent condition to 'Knuckle Line'
The second curve now displayes a knuckle as if the attached control point had had the knuckle point constraint applied. Any referencing curves to the first would display this behaviour and removes the need to apply individual constraints to each referencing control point.
Creating a Simple X-Topology Surface >>>