This post is a reference of most often used Rhino commands for manipulating curves.
Most of the commands to edit curves (lines) are very similar to the ones in AutoCAD (and they are called exactly the same). See the following video that demonstrates commands such as Trim, Extend, and Join.
Fillet = rounded corners: this makes it easier to remember. There are two commands we can use to round corners.
Using Fillet (first used in below video) you round each corner separately, one by one.
FilletCorners works on all corners of selected curve at once (in video, applied to the curve on the rigtht). In both ways, you can specify the corner radius either by writing it down, or by picking two points on screen (the radius will then be the distance between the points).
Offset (at the end of video) works very similarly to AutCAD’s offset:
Sometimes you’d want to move the line points directly to adjust the line shape. To do this, use command PointsOn which will reveal line points, and then you can move and rotate them as if they were any other object. Please note in the video, for example, the use of Gumball to scale the points which distorts the shape symmetrically:
If you need to connect two curves by a smooth segment in such way to maintain curve continuity, use command BlendCrv.
Rhino doesn’t allow us to draw a curve that will have sharp corners, nor it allows us to change the control point of the curve from “corner” to “smooth” – as it’s possible to do in Illustrator, for example.
So in order to create a curve with sharp corners, best way to do it is:
For example, if we want a sharp corner on this fabric softener bottle:
If you have a line that you want to “project” to a surface (for example, to cut the surface with it), then you should use command Project. Please note that Project will project the curve using the normal to construction plane. So you either need to rotate CPlane in position normal to projection, or use some Ortho view (ie. Front, Left, Right…).
Sometimes you have a line (curve) laying directly on the surface (maybe you extracted it from the surface – see below, or projected it onto it….). If you want to perform such an offset to the line that the line maintains on the surface, use OffsetCrvOnSrf command.
Almost all surfaces are created from curves (lines) one way or another. What if you want those lines back? There are several methods to extract curves from surfaces.
Iso curves are the ones that exist in surfaces that are created using commands such as Sweep1, Sweep2, or Patch (many more!) where the surface is defined by a network of curves usually going in two directions (ie. one direction is the rail, the other is the profile). You can use ExtractIsoCurve to extract those curves from such surfaces. You can pick whatever point on surface that you want the curve extracted – also note you can pick the direction.
Sometimes you want to extract boundary edge. This is easily done using command DupBorder that will create lines for all borders of the selected surface: