Best way to draw on an object

If I am creating an object that has (for example) a cube and I want to draw a circle on one side of the cube.

Is it best to change the Cplane to the side that I need the circle on and then draw the circle?

I have tried this without changing the Cplane and it looks like I am drawing the circle but after I hit enter the circle disappears and I have to go searching for it.

I think it will draw it on the current Cplane, is that correct?

It does not seem consistent either if I don’t change the Cplane - I built a fey cylinders on top of each other (different diameters) cylinders seem to build on top of each other but a 2D circle does not.

So, what is the best way to draw an object on an existing object?


Hello again,
Maybe I can ask this a bit simpler.

If I draw a cube and then want to draw a circle on each side, is it best to switch the Cplane to each side to draw the circle?
or are there other methods?

Thanks again!

My personal workflow would have me do this in a perspective view with Project-off and Osnaps all on. I avoid setting the Cplane to anything other than the defaults. (hat’s just a phobia I have).

In the attached example, I drew the circle on the cube top with the circle command-default, using SmartTrack to find the center and then clicking a midpoint on the top edge. I drew the circles on the sides with the circle command and using the 3-point option and then clicking on midpoints of 3 edges.


Cant duplicate that.
Every time i go to draw the object draws on the cplane.


I figured it out…

Use the different viewports…

I got so used to using the Perspective viewport only…


I drew this in the perspective view only. The key here is to make sure “project to cplane” is off. (and your osnaps on)

I have my F2 key set to toggle it on/off…

ProjectOsnap T


And supposing the circle isn’t exactly the size of the side nor centered on it…?

I often use CPlanes - either something like Surface or Object, or 3Point when I need an exact origin and direction. My advice is only change the CPlane in your Perspective viewport…


Good point. I just work around setting custom cplanes. Like I said, it’s a phobia.

I’ve never understood why, but it seems, that setting a custom cplane in the perspective view replaces the default one and every time I switch to another view and then back to perspective, the custom cplane is back.

It drives me nuts when I open a Rhino file that one of the guys here has worked on and has set a custom cplane. I’ll try moving stuff around in the perspective window and the axis will be switched to this cplane so transforms all work wrong. Resetting the cplane to WorldTop only seems temporary and the custom cplane keeps resurfacing like a bug or something.

I think therapy is in order…


Jim, in options->view do you have ‘named views set cplane’ ?

That is correct. CPlanes are a document property set by view and they stay that way until reset - even if a file saved, closed and re-opened. So you need to remember to set it back or reset all views to default…

It shouldn’t once you have reset it…
Using the command 4View twice will also reset all CPlanes (and default views) back to defaults.

I also have the following macro to “reset” my perspective viewport:

_SetView _World _Perspective _Zoom _Extents _CPlane _World _Top



Can you please clarify what you mean by:
“Using the command 4View twice will also reset all CPlanes (and default views) back to defaults”

What is “4View”?


It’s a Rhino command… It sets the Rhino window to four viewports. Try typing it at the command line… It’s also in the Viewport Layout toolbar. See the Help entry under the command name…


Thanks Helvetosaur. That’s good to know.

Maybe I never discovered how to reset the cplanes because I never use 4view. I just keep one full view open at a time and switch back and forth. I’d think there would be a resetcplane command…


Continuing along the CPlanes idea is a Rhino setting called "Universal construction planes"
The control is in Options - Modeling Aids.
When “Standard construction planes” is selected, the CPlane in each viewport is independent.
When “Universal constructions planes” is selected, the CPlanes in the viewports are linked. If you change the CPlane in one viewport, the CPlanes in the other viewports shift as well keeping them all with the same origin and at the default 90º orientation to each other.

Thanks Mitch,
I didn’t know about the “twice” option.

good stuff…

I’m new to Rhino.

I have a sketchup background when it comes to 3d modeling. In SketchUp it automatically detects the plane on which we want to draw a polygon. Changing cplane every single time is very tedious and mind-boggling when we want to draw a surface which is inclined or vertical. I first made a box and my smart track is also on but I’m getting unexpected results while trying to draw a circle. Please help

Having this kind of automatic “cplane based on the hover position of the mouse” would greatly improve some sketching workflows! Sketchup is most famous for this, but AutoCAD as well has a “dynamic UCS” modeling aid which is essentially the same: dynamic UCS in AutoCAD | CAD CAREER - YouTube

Just to check, because Rhino is a box full of surprises on doing things one actually didnt think it could do: is such feature available in Rhino? (of course, I think it would only work in meshes). Thanks!