Thanks Michael. An Orient Transform tool sounds interesting. If such a tool would be much more versatile than my suggestion about a copy / paste option, then I hope you get a chance to work on that soon. It would be useful to me for the way I think and work with shapes in 3d.
Thanks for your suggestions on how to work in the meantime. In addition to those, I found another workaround which is a little complicated by has some distinct advantages over the others. It may be helpful to others. I wanted to place copies of a profile curve at specific points along a rail curve in 3d space. 1) Construct a curve in 3d space. 2) Use Pick Point on the Draw Curve pallet to place a point on the 3d rail curve. 3) Use Copy on the Transform pallet to place other points at specific locations along the rail curve. 4)Draw a profile curve comfortably outside of the bounding box of the rail curve so that you can later use the auto-place mode using the sweep command. Select it and note its dimensions in the upper right of the UI. 5) Use CPlane on the View pallet to set a plane origin at the first Pick Point. The default orientation of the X,Y and Z axes when placing a Pick CPlane origin on a curve is such that the Z axis is tangent to the curve at the origin. 6) Use the Plane tool on the Draw Solid pallet to center a plane on that pick point. The plane should be comfortably larger than the dimensions of the profile curve which you noted earlier. 7) Continue using the CPlane tool and the Plane tool alternately with each of the other Pick Points. These constructed planes should each be parallel to the tangent of the 3d curve at the point at which they intersect the curve. 8) Select the profile curve and Sweep it along the rail curve using the auto-place mode. While using the Sweep tool make sure that Cap Ends is not checked so that the sweep will create a surface rather than a solid, and I suggest setting the Twist to Freeform. 9) Select the newly constructed sweep object and using the Boolean Diff tool on the Construct pallet, select each of the constructed planes which intersect the rail curve and subtract them from the sweep object. (Some other Boolean operations may work as well.) 10) Without selecting the surfaces of the sweep object, select the edges that were formed by the Boolean operation. Use Copy tool and the Paste tool on the Edit pallet in order to create curves from these edges. 11) Select and Delete the segments of the sweep object surfaces. These curves are nearly identical to the original profile curve. They can be easily rotated and scaled before selecting them in sequence and sweeping them along the 3d rail curve to form some very interesting and beautiful shapes. The major advantage of this method is that MoI does most or all of the job of rotating if Twist is set to Freeform when doing the first sweep. The disadvantage of this method is that the created profile curves differ from the original in that they have hundreds more control points which makes tweaking the shapes using control points very difficult.
If you need to have identical profile curves, that is, having the same number of control points, The following method seems to work (I am not sure how or why): Create the original profile curve on the world XY plane, usually using Top View. Create Pick Points at any specific points along your 3d rail curve. Use the Copy tool on the Transform pallet to place copies of the profile curve at each pick point. Keep in mind as you select the base point that, when the profile curve is re-oriented, the rail curve will run through that point. Place the Pick CPlane origin on any specific point along the 3d rail curve. [It is critical that the default orientation of the Pick CPlane origin snaps to “point” If it snaps to Center or some other point on the profile curve, EVEN THOUGH IT OCCUPIES THE SAME POINT IN SPACE, it will affect the orientation of the CPlane axes. You may have to temporarily Hide the profile curve or disable some of the snap options. It does not work simply to orient the new CPlane Z axis to be tangent to the curve at that point.] At this point it requires only the one following rotation to orient the profile curve so that it lies on a plane perpendicular to the tangent of the curve at that point: After setting the CPlane Origin at each placed Pick Point, and switch to Right View, the profile curve will be viewed on edge and will appear as a line. Using the rotate tool pick the Origin as the center of rotation. Using the Right Viewport, Pick any point on the profile curve as the first reference point, remember that the profile curve will appear as a line. As the second reference point click any point on the 180 deg horizontal of the Right Viewpoint. The snap should read “180, Tan , Perp”. Again, I don’t know why this works, but it will work for every point and every change of CPlane orientation as long as MoI is free to choose the default orientation.
Thanks again, I appreciate all the hard work and genius (and wizardry) that goes into MoI.
Dan