I need some advice creating smoother, more uniform curved surfaces


Hiya folks, I hope you are,

Am currently creating 3D models based off artwork to improve my 3D modelling skills in Rhino, am currently struggling creating the shoulder pad on the robot pictured below. I’ve reworked it a few times but am struggling to create something uniform, smooth and rounded, I always end up with kinks, bumps and such.

Any advice on how to better achieve this shape?

I am currently creating the shape by drawing it up curves, sweep2 those curves, mirror and join the surface then offset to create the thickness.




Post the .3dm file of your model. You can upload it using the vertical arrow above where you type your post.

Also check your mesh settings in DocumentProperties > Mesh. “Jagged and faster” can result in a display with sharp corners and gaps between curves and surfaces. Try “Smooth and slower” or “Custom” with the slider moved to the right instead.


heart bot.3dm (5.1 MB)

Here you go David. My mesh are fine and are as you already suggested :slight_smile:


I exploded the pad and the outer surfaces go past the center plane of symmetry and are trimmed back to the center. Rebuild those so an untrimmed edge is on the plane of symmetry and then you can use MatchSrf to match tangency which will also match curvature when matching symmetric objects on the plane of symmetry. MatchSrf can only change untrimmed edges.

I also made a surface using the curves in your file. Tried Sweep2 but it had a bump. Tried NetworkSrf and got a nice surface. Some folks might prefer to make individual surfaces using EdgeSrf and then MatchSrf those.heart bot DC1.3dm (4.8 MB)

(Marc Gibeault) #5

The basic principle to maintain continuity when modeling half of the model is very simple;
You have to make sure that the geometry has at least one control point in line with the point of intersection.
In the case of construction curves, like you showed on your first post, one control point must be in line with the point lying on the mirror plane:

Purple is helper geometry, green are my construction curves, red are the mirrored curves.
Cyan lines shows the control points that are in line.
One point in line = at least tangancy continuity
Two points in line = at least curvature continuity


Thanks for the effort David, much appreciated!

The surface looks great but unfortunately it doesn’t off set nicely

I presume that will be down to my initial geometry not being as desired


So just to clarify Marc, 2 controls points lined up will always ensure curvature continuity?

Like below

(Pascal Golay) #8

Hi Marc -
This is true in a limited way, if I understand you - that is, if the end points and the next two points of two curves that meet are all in a line, you will get curvature continuity but at the expense of that curvature (where the curves meet) being zero. Not sure if that is what you meant.

(On the other hand, if two curves are mirrored copies, G2 comes for free with tangency matching.)


(Pascal Golay) #9

Hi John - is the set of curves at the top of your images what you are using? What are you getting those from? The thing looks close enough to a revolved surface and/or a deformed revolved surface that I’m just wondering if it can be simplified as in the attached - I’m not sure I worked on the right part…

heart bot_PG.3dm (121.0 KB)



So sorry about the massively late reply! I went on holiday and then totally blanked about the topic.

What you’ve created Pascal is spot on, I brought it into my model and it need a couple of mins tweaking to be exactly, so thanks, much appreciated!

Do you mind talking me through how you created it? You’ve lost me at deformed revolve in all honestly :stuck_out_tongue:

Also Pascal, when G2 comes free with tangency matching, is the tangency matching part of the mirror or symmetry command?

Thanks again


(Pascal Golay) #11

Hi John - see the attached file. The shape looks like it is based on a revolve of one arc - I made two - one stays put, red, and the other is modified by

  1. ChangeDegree to 3 in the U (around) direction to give it a couple more points.
  2. Move points making sure to keep the points aligned across the quadrants of the revolved surface - that is, unless you Rebuild the surface (which seems unnecessary here) you must move the points in a constrained way to keep the tangency at the quadrants.
    heart bot_PG_plus.3dm (136.2 KB)



Thanks Pascal, that makes perfect sense!

Was able to model his head in similar fashion, something I had been struggling with :slight_smile: