Merging and smoothing bodies (general question)

So lets say I’m working on an organic design (call it a rubber ducky) that I’ve started by approximating with these two bodies. The step I’d like to reach is where I can rebuild the resulting surface and tweak it with control points, but before that I’d like to “smooth” out the neckline here where the two bodies meet. Essentially I want to add a fillet except that my experience with Rhino’s fillet tool is that its…temperamental, and I’d appreciate any advice

Use BooleanUnion first to make one solid with an edge along the intersection. Then FilletEdge using a radius which allows enough of the adjacent surfaces to remain for the trim and join portion to work. This last bit is usually why you don’t get the result you expect. In this example, a fillet radius larger than the distance to the ellipsoid seam would require a blend not a fillet as it could not be smoothed out with a single arc.

and if the fillet is too large it crosses the seam and can’t trim because it isn’t flowing down along the surface it’s trimming…

That’s when a trim followed by blendsrf works better…

Also, you say that you first want to smooth out the neck region, then tweak the shape of the ducky. To prevent having to perform the fillet or blend over and over after each change to the shape, you can try to enable History (Bottom of the screen “Record History”). Any changes to the input surface of the fillet/blend operation will result in the creation of a new fillet/blend on the updated surface.

Thanks! Very useful tools there. Rhino’s surface editing tools are just so dense that I usually have no idea where to start

Hi Menno -

You wish!! =) Fillets (FilletSrf, FilletEdge) and blends (BlendSrf) are not yet part of the History system I’m afraid.


Oops, I stand corrected :smile:

Alright, so after doing BlendSrf I’d like to MergeSrf if possible but it says it can’t do trimmed surfaces? I looked up some stuff that implied that it was because the underlying geometry of the pre-trimmed solids was still there? Is there any way to convert these surfaces such that MergeSrf would work?

Aside from rebuilding the surfaces with untrimmed versions, no. Think of all NURBS surfaces as being four sided pieces of infinitely stretchy graph paper. There are always four sides even if one of them collapses to zero dimension as in Sweep2 to a point. MergeSrf matches up the grid lines in the graph paper and makes them one surface but when you have a trimmed surface the graph lines (UV directions) won’t match up.

This is an active feature request to handle however so it is on the radar. In the meantime, BlendSrf is great for matching continuity across trims but you will have a polysurface once joined.