Revolved Surfaces


Why when a curve is revolved to make a surface do we get the join showing, in the image I have hidden the revolved curve so to me I dont want the join to be shown. I know I can go into options and hide all edges but that affects the whole model and may not suit, I want to hide the join / seam not necessarily the edges around the item

Have you tried , in display panel, to uncheck " tangent seams" ?

Hi Cyver, That is exactly what I needed, even checked back in V5 in case I missed it there but could only find it in V6 so dont feel so daft now.

Hi any suggestions for the seam along the pipes they were created with the Pipe command and I can only get rid of them if I use edge thickness of 0.

You also have “tangent edges” check box, in display panel.

Or try to avoid kink control points by rebuilding or refiting curves, but not always possible.

Hi Cyver
you will see in the bottom screenshot I have tangent edges turned off and the lines remained until I set edge thickness to 0. I had no input into the pipe command other than providing the basic info required by the routine.

Don’t know how you build your curves , but seems those edges behave like surfaces edges not like tangent.

if you want to hide all edges, open the display panel on your right, right click on any tabs ( where properties, layers etc… are ) , and check “display” , you will have a new tab with all displays options, uncheck surfaces edges.
hope that help .

Hi Thanks for the answer which is really what I was wanting to stay away from as that affects all edges in the model, I’m still not sure why the Pipe command makes that an edge in the first place as it is basically extruding two circles. Even if you extrude planar curve the seam effect is shown as an edge, personally I would rather we didn’t get that from any extrusion.

A circle has a start and an end. Any NURBS surface is basically a rectangular piece of ‘material’. There are always 4 edges.

That said, when I use Pipe on a curve, I can turn off the seam without turning off other edges - can you post your file?

Tangent Seams and Tangent Edges:

Tangent Edges only:

Only non-tangent edges:

Rhino V6 Test 1.3dm (69.8 KB)

Hi Wim, here is the file created in V6 just using the pipe command, and the seam along the side can be seen on all 3 sections. Thanks for taking a look.

Your straight pipes are extrusions. They need to be polysurfaces if you want to hide tangent edges. Extrusion objects don’t obey all the display rules…


Cheers Mitch, I’m always learning I will have to change my approach if I can.

UseExtrusions allows selection of whether extrusions will be created where possible, or if polysurfaces will be created.

ConvertExtrusion converts existing extrusions to polysurfaces.

It sounds like you don’t perhaps understand the underlying topology of NURBS surfaces. You’re describing things in terms of the physical object these NURBS surfaces represent to you, like a “pipe”. Pipes generally do not have “seams” but NURBS surfaces do.

The basic underlying form of a NURBS surface is a rectangle. If you roll the surfaces into a tube and Join the opposite sides of the surface, this in NURBS terminology is a “seam”. This is the line you see running down the length of your pipe.
If I add capping surfaces to the tube, these are rectangular NURBS surfaces that have been trimmed to be shaped like a circle. If the edges of the surfaces are Joined, you have an “edge”.
Instead, if the circular “naked” edges of the tube are shortened down to a zero length, you have a “singularity”. This is how you get a sphere made from a single NURBS surface. Two opposite edges are Joined into a seam, and the two open circular ends are drawn up into zero length singularities.

The Rhino display options described have tools for hiding the display of these seams, edges, and interior isocurves.

Yes, but @John_Brock they do not appear to apply to extrusion objects, which looks like part of what the OP was seeing anyway.

Extrusions are strange objects. It doesn’t sound like they are helpful for this user. They really are only handy for architects make lots of very simple objects. That’s who they were intended for.

For everyone else (including myself), I recommend turning off using extrusions with the UseExtrusion command.

I just added this:

Hi Thank you for all the info it has been very informative, the reason I use “Pipe” is that it is easy to script which generates a perfectly adequate CAD entity for our purposes even though it is an extrusion.

Hi Thanks for the command ifo, if I convert my extrusions to polysurfaces I can get the desired affect that Im looking for, happy days thanks again.

So why isn’t it off by default? --Mitch