Welcome to 3DCADForums

Join our CAD community forums where over 25,000 users interact to solve day to day problems and share ideas. We encourage you to visit, invite you to participate and look forward to your input and opinions. Acrobat 3D, AutoCAD, Catia, Inventor, IronCAD, Creo, Pro/ENGINEER, Solid Edge, SolidWorks, and others.

Register Log in

NX: Help with free form b-splines, convex curves, and parametric law curves

Vincent Zhang

New member
Hey so im trying to make a waterslide. Can anyone knowledgeable with splines in NX help me figure out how to make these three sections

Your waterslide (and therefore the space curve) must consist of at least three sections:
the entry free-form section, (the parametric) serpentine section, and (the exit) convex
free-form section, as described below.
• The entry to the waterslide is a free-form (B-spline) section that must pass through
at least 4 non-coplanar points (i.e., they cannot all lie on the same plane); you
can use it to design a variation of a “toboggan” slide.
• The serpentine section must be created using an explicit parametric law curve.
The easiest way to do this is to pick any planar parameterized curve, such as
those that can be found at
and add the third dimension by specifying z(t), where t is the parameter of the
planar curve. Recall what we did in class for the circular helix, and what you did
in the lab with the involute profile. Please do NOT use a circular helix for your
serpentine - pick a more interesting shape.
• The last section of the waterslide is a “convex” free-form section (holds water,
and is another B-spline). This is your exit flume.
• You must be able to perform a rough analytical estimate of the total length of
your slide, and later verify it using tools in NX. You can approximate the lengths
of the free-form sections but you must compute analytically the length of
the serpentine section - see below.
2. It may be easier to position the end of the exit flume at {0, 0, 0} in the absolute
coordinate system, the positive z-axis should point upwards, and the xy-plane should
be considered ground level.