World-Aligned Circles / Cylinders / mid-point snap

today in the classroom with 6 Rhino-Novices.
It s always a very valuable moment to see where the participants struggle:

As an introduction for Boolean-Operations I use this object:

I think it s a big pity, that circles, spheres and cylinders are drawn with a rotation by default.
(with rotation I mean the position of startpoint / curve-seam / surface-seam)
I really would appreciate, if the default behaviour would be to have those objects aligned to the current c-plane.
my wish would be to always have circular objects having there start in relation to the positive x-axis of the current c-plane.

The bad thing is the combination with a mid-point snap on a default (extrusion-)cylinder.
The displayed pseudo-Isocurves have a mid-point-snap (why?, surfaces don t have this) - which leads to errors for the next modelling-steps - for example rotate …

if my non-native-speaker english does not describe above problem precise enough - try to model above object.
for the diameter of _sphere and _cylinder use a visual (non-numeric) value
nobody in the beginner-classroom managed to have a nice rectangular isocurve / surface-seam layout on the final object.


  • use apparent intersections should not be checked by default
  • circular objects should be rotated according to current c-plane (always/ default - people who need a rotated object can rotate it, or set the cplane, or do an option / preference to enable free rotated circular objects)
  • Cylinder (Extrusion) Isocurves should not be snapped by default (kill this options or make it a preference that is turned of by default)

thanks - kind regards -tom

Hi Tom - this behavior change - orienting according to CPlane - would be something to consider, is the most I can say at the moment. There may be all mannrer of workflows where the seam location is important - there would be a trade off there, perhaps a significant one, where, possibly, novices might be spared some pain, possibly, but existing users would need to re-learn.

What is the goal here? Or, what is the problem, I guess, is the better question?

Meantime, there is always the Quad OSnap.


Or Ortho with 90° set, which will at least orient the seam in one of the 4 cardinal directions of the active CPlane - depending on which way the mouse is pulled.

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The benefit of Quad OSnap is that it snaps to the quadrants of circles and cylinders as they are represented relative to the current CPlane. This means that you can choose how you want your circles oriented for snapping by changing your CPlane.

I think this is a much more powerful tool for circular shapes than intentional orientation, but it is yet another tool to learn.

thanks @pascal @brian @Helvetosaur

yes I teach quad-snap.
and I teach temporary ortho-snap (shift) to draw c-plane aligned circular objects. (as Mitch wrote)

but the bad thing to consider:
it is hard to evaluate wether the circle was drawn right. many students draw it visually and result with a 89 degree or 91 degree orientation…
which will lead towards end-snap and quad-snap quite close to each other - or easy to fail to get it right.

I teach one workflow / example where this is the case - a fillet exercise with 2 tangential cylinders stuck on each other. And I teach to rotate the cylinders to be sure their surface-seam is correct.

my guess: the majority of users will profit from c-plane orientate circular objects.
so maybe this is an option / preference ?

… just wanted to send some feedback where new users stuck - for me it is always a important “testimonial” setting.

Without a mouse input, the seam ends up on the X-axis. At least in Rhino 8 BETA.

No, it has been like that as long as I can remember. For circles, X Axis is 0° and it goes CCW from there.

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I have not tested in Rhino 7