Working with planar sections curves in 3D space


I run into this situation from time to time where I have planar sections that will be used to loft or sweep, but keeping them planar is not easy (while editing them).

  1. I figured out that if I create a new CPlane aligned to the section, I could keep them planar, but it is kind of tedious to draw a new CPlane every time I want to edit the section curves. Is there a better way?

  2. Lets say there are multiple rails/geometry I want to snap to while working in the local CPlane. Is there a way to snap to where the rail/geometry intersects with the CPlane? Is there a way to intersect the rail with the CPlane? Currently I have to draw a surface on the CPlane and intersect with it.

161202 Temp1.3dm (61.5 KB)

i am not sure if it does intersect to cplane not that i ever manage… but you can activate project and it will draw along the cplane no matter how its rotated. further you can also create a quick surface this surface can also be bent or shaped into any twisted direction of your desire then check on surface after you activate a drawing command and it will precisely draw along it.

The problem with the project method is that the curve could be snapping to any near position along the curve while projecting. Only the intersection point is correct.

Yep - that is about it I’m afraid. Add points that way and snap to the points. You can set CPlanes snapping to the Ints of the rails and section curve, and save the plane so you can get at it more easily next time (NamedCPlane)


A little different but related, when I loft/sweep a surface, the control points are usually very neat and organized. Is there a way to move them normal to the surface? I know I could draw a line normal to the surface and use it as a directional guide but that seems tedious.

Yep - MoveUVN or set Gumball to align to ‘Object’ - then surface points will show the blue arrow in the normal direction. Also, DragMode can be set to UVN or ControlPolygon - then Ctrl-drag on control points will move them normal.


1 Like

Thanks @pascal

Great tips .

Just curious, does moving a control point normal to a surface keep the normal direction the same as it is moved, or does the normal direction change as the surface is modified in this manner?

Hi Nick - not necessarily - probably rarely, but as a simple example - take a plane that is in the CPlane and move a corner point normal (= vertical). The normal at the corner can no longer be vertical to the CPlane.


Ok, thanks Pascal, that makes sense…