Can one pre-indicate to system which line to use in Circle TanTanRad?

Circle TanTanRad
Problem is not just this but other commands requiring lines or circles etc planar on same plane.

In my issue prompting this post,. First line is the only line and is on Cplane, then second line though sees a few exist in the same place, and all but one are not on Cplane.
I choose Circle Tan tan Radius, select the first line, then select the next (no options appear as to which one, else I could go by colour), then I enter radius and hit enter and no circle appears.

Classic case of both lines need to be planar and its chosen one of the non planar not on cplane lines.

I am left no option but to move my lines e.g. r-1000,0 deal with out there then r1000,0 it all back again !

Can one select the line to be used of the second click, before running the command, or how does one make sure the right line is selected ?


Hi Steve- use the OnCrv one-shot Osnap. Does that do it?


Hi Pascal,

Command advice for that says only available when picking points, I am selecting a line.
CommandHelp doesnt show anything on it.

Its as if the coomand fails, it deosnt then ask me to do anything.

When would I run that command before the tan tan rad ?

and now I have another task again hitting agaionst this issue:-

I have a line on Cplane, though another matching it in ortho view Not Cplane, fortunately I can use the Cplane line, however the next line I need to pick is not cplane, and the command requires it to be on Cplane, how can I handle this situation ?

Command in this case is Draw line perp from curve.

I had to go to perspective to start the command pick as it didnt know which line, the Cplane or the non Cplane to start from ! I wish I could choose an option in command line before the first pick that would apply to all picks in the command that says pick assumes curve Cplane (i.e. Rhino ignores its actual plane and treats it as if it was Cplane)


So you did not even try it? Type OnCrv and Enter when picking the tangent point along any of the curves. Any luck?


Somehow I think most of this stuff is simply related to drawing management - using layers, locking, hiding etc. in order to isolate different sets of objects you need to work on, and using the perspective 3D window to make it easier pick objects not on the same level instead of trying to figure out from a 2D view of multiple overlapping objects which curve is which - that’s what it’s made for.


Hi Pascal,
I didnt realise it was to be typed in during the command, I forget that you can have a command within a command.
Yes it works, odd though, the command normally asks for two curves to be picked and then enter radius.

This time it asked for a third tangent, pressing enter draws a circle through a point created after the first line is selected. To get round this I see one enters R instead of worrying about what third tangent it wants, then enter the radius value and you get a circle of your required radius.

In summary OnCrv in use with Tan Tan Rad circle tool asks for third tangent, so ignore and enter R and you get the command as one is used to.

I shall add that OnCrv to the list of essential tools now in my brain :slight_smile:

Hi Mitch,

Turning off layers to get at what I want, comes into the territory of my plea for select object indicates layers. I have many many layers, many colours, an extremeley complex build. If I was to select objects, view properties, find layer in layer palette, turn it off, repeat that 20 times or more , make notes of what was on and is now off, then turn them all back on again, the finding the layers stage of that would take half an hour, finding them again just as long. Nightmare.

Could I select the ones I dont want in perspective and use a command to lock them, then after running the command I do want, e.g. tan tan rad, select them and unlock them. Without going anywhere near having to find their layers ?

I do use perspective view to get at exactly what I need, there are times however that picking in that view, then reverting to an ortho view sees command fail. I found that to happen when projecting lines to a surface, it refused to work unless I started and ended in one window. It made choosing the stbd aircraft skin when the port one was nearest me very difficult ! Maybe it shouldnt do that but it did to me.


All osnaps can be invoked at the command line within a command- for ‘one shot’ osnaps like OnCrv, they can only be activated inside a command. You do not need to type them- you can make buttons, or use the Osnap toolbar: If you hold Ctrl while hovering over the OSnap toolbar, you will see the available ‘one shots’.


Hi Pascal,
I never knew that…run tan tan rad, hold ctrl and as you say the one snaps show up when hovering the OSnap toolbar.

I would like to know who else never knew this.

Clearly there is still lots I have to learn in Rhino.

I worked my way through both tutorial manuals, understood everything, head on duck, bottle of something etc, never recall seeing that. No doubt one forgets some things.

I bet there are things that would make life easier, its knowing about them.

What training vids are there beyond the Rhino training dvd I obtained with V4. Rhino visual tips I think it was called. I am sure that was not in there. Time to sit and view again would be nice.

Obviously we are now V5, well I will be when I can get this current job done.

I want to learn and learn, and wish to have something from McNeel to learn to, not rely upon variable quality YouTube vids.


Steve, if you do a tiny RMB pan when you go back into the Orto viewport, it will activate the viewport and the object will remain selected.

Also, are you aware of the commands, OneLayerOff, OneLayerOn, LayerStateManager, Undo and Help… They should make your workflow a bit easier.

From your other Layer post, you could regain your evenings by docking your properties panel beneath the Layer panel, then you would see at a glance which layer your picked object is on, and change its properties if required. This won’t be necessary in V5 when you finally get there as the selected object layer is on view in the status bar (providing the layer name is not too long)

With regard to your disappointment with the training material available, your best option now is to build experience with real jobs - as you seem to be doing.

Occasionally, in those cases, I just open an extra Rhino, cut geometry from the main file, work on that in the temp file, and cut and paste back into the main file when done.

I suppose I could be using workspaces for this but I feel it’s more simple this way…