Here is a Houdini asset which generates a continuous quarterpipe from a user drawn spline. A number of stroke attributes are stored on the user spline based on the pressure of the wacom pen. These attributes then drive an appropriate height and curvature value for each point on the user spline.
Each transition curve is then copied onto the user spline and are skinned together. From there the top and back parts of the transition are separated to generate the top deck, coping and boundary railing.
There is also an option to replace the stroke pressure attribute via the Ramp which is mapped from the first to last point on the user curve to create custom elevations.