Tuesday, October 12, 2010
A helix is actually a very simple shape for parametric modeling. Think of it as a segment of a shell that is rotated and translated (offset) with each increment. You can make one in Autodesk Revit very easily.
Create a family with a generic model. You can make an extruded box drawn in an elevation view. I drew a reference line to define an angle through the family center. Rotate the box to align with the reference line. Create a parameter for the angle. Make sure that its type is "angle". Draw a angular dimension on the reference line and associate it with the angle parameter. Create an index and a angle_increment. Create a formula for calcuating the angle of rotation from the index and angle increment. That's all there is to the family. (I have added some extra parameters in anticipation of changing the radius of the helix and the size of the patch.)
In a project file, you can insert the helix facet. Insert 20 or 30 copies. Change the index of each copy and it will spin around the axis to the right location.