Keeping it simple?

I’ve made a pair of curves to run a two rail sweep and while the curves are are only degree 2 with seven control points, I end up with a surface that has six times as many control points on it’s edges - the very edges formed from the simple rails!

When I next go to blend this surface it generates 240 surface points and makes smoothing or matching the surfaces a pointless (pun) exercise.

ArgoFlex6.3dm (823.2 KB)

try using EdgeSrf for that curved_vertical surface instead of sweep2… you’ll probably like the results better.

Much better! But still this. What’s with the bunching up?

For the vertical wall use Sweep2 and select the “Simple Sweep” option.

1 Like

maybe change up the approach? make larger surfaces and eliminate the middle horizontal curve from the equation…
a couple of ideas for starters:

draw the straight parts first using a single profile curve for each section (or an arc joined to a vertical line etc.)… as in, draw the profile curves then use ExtrudeCrv on them… get rid of the curves going through the corner…


from there, you could try BlendSrf :


or you could try BlendCrv then NetworkSrf


i think both of these methods would give you smoother results with much less work / tinkering… as in - see the thread title :wink:

1 Like


I think Lofting instead of using Sweep will get you to a better result without a crazy amount of control points. Create your middle curve first, the make a copy of that curve and use SetPt to flatten that copy. Loft between the mid curve and bottom curve, then create the Blend as usual, if you need to increase the degree of the top cap curve you can run the change degree command. You should be left with a fairly controllable blend at that point, not great but not impossible to control either. I’m not positive about this but I don’t think you have any continuity controls with Sweep. Hope this helps.

Thanks Jeff. The problem is complicated because I’m trying to blend two different radiuses from four directions. See attached. Making things as simple as possible…? I figure it’s best to try and blend the two surfaces with G3 matching the pattern arcs from thier quadrants. This is why there’s a blended line at the midpoint and what gives me the single surface to blend to.

So I get something that looks okay but not great - that is the sharp edges you can see the in the last shot. Maybe that’s the best that can be achieved with the constraints I have?

Oh god when will this end? Why not just make a simple solid then run a variable fillet/blend around the edge?

The simplest solutions are always the best.

Like this?:grinning:

Or is this more like it?


Here is a snapshot of a few models, all done with just a few commands, Blend Curve, SetPT, Loft, Surface From Planar Curves, Blend Surface. Your model is far right, and the only difference between the middle and left model is the tangency and curvature continuity options on the surface blend. Filleting in Rhino is going usually going to cause you more problems than it’s worth.

At least make an effort. You are obviously going to need to increase the corner radius to allow the fillet to flow. Just use the one in your existing model.

Being dismissive is good to way of discouraging forum members from helping you. Don’t count on getting any help from me again.

Look, Stratosfear - Opening your ‘contribution’ with “Oh god when will this end?” doesn’t come off very encouraging, and in any case, I didn’t ask anything of you personally. You injected yourself and your peevishness into the discussion.

Furthermore, I tried your recommendation and is makes a mess. It’s not simply a matter of “obviously” increasing a corner radius that will allow a fillet to flow or just doing a few simple commands and accepting what the program decides to create.

It’s a matter of working to a number of constraints that will accurately reproduce an item that exists in the real world. Developing this ability is I think desirable for future professional endeavors. I don’t mind doing something over and over until I get it right. And as far as I can understand, this forum is open and free for any and all to participate to whatever extent they wish.

As you can see, Tex didn’t have any problem helping me out, nor have countless others. At some point in the future I may be able to contribute as well.

Be nice.


1 Like

They look beautiful. I am awed. Did you build these in Rhino or MOI?

Hello JKayten,

In Rhino. I used a similar method as described in the video I recorded with a few tweaks, but the procedure shouldn’t take you more than 5 minutes. I should have time over the weekend to post a video of the procedure if you like.

Is this how you handled the lower curve that’s blended from the two horizontals that run through the quadrants of the radiuses? Blend then set points? I’m not sure how to set points in that case regarding the orthos.

5 minutes is an ambitious time trial for me at this point, but I’ll eventually get there. I understand that you accomplished the results with the curves from the file I sent you? You gave me a number of tools to use and I generally understand which was used for what was needed. I’ll review the vid you made and see if I can accomplish this thing. If you’re inclined to make a video this weekend it will be very welcomed. In any case, you’ve my undying gratitude!


Hello JKayten,

I used your existing lines and recreated the bottom capped curve (tangent and increased degree to 5) and the middle curve (looks like G2?), then copied and flattened that (using SetPT) to create the planar curve set to loft. I do notice that your line work is slightly off but it could be due to the precision I am working with (not sure)? I’ll make a video and it will make more sense. Glad I could help.

The front is set back from the zero line by .25 mm. I have to add a ridge that depth to the front of the form that blends into the side. You may be able to see that in the images. I’m working at the template precision of .001 mm. Pascal gave me some instruction on the issue of degree settings and using edgesrf to create a corner in an earlier portion of this project. I’ve been looking for some instruction on the theoretical as well as practical aspects of various G ratings and control points count.

Your transition modeling challenges very likely originate with trying to model the camera using a higher level of “smoothness” than it actually has.

Your camera was probably originally designed with straight lines and simple circular arcs, flat surfaces, edges which were cylindrical, and corners which were spherical. Simple arcs and straight lines are excellent fits to the curved corners and straight edges in your photographs of the camera.

G1 is the highest level of continuity geometrically possible between a straight line and an arc, a flat surface and a cylindrical surface, and a cylindrical surface and a spherical surface. This is basic geometry, not a Rhino imposed restriction.

Forcing a higher level on continuity such as G2 between such curves and surfaces generally results in regions with higher curvature near the transitions. In order to maintain the same radius over most of the “corner” and have G2 continuity between the corner and the flat surfaces the arc/cylinder/sphere must be moved in and the transition zone extended into the straight line/flat surface area. Again, this is due to basic geometry. This type of surface refinement is non-trivial, and not a good exercise for learning the basics of “smooth” surfaces.

To effectively model your camera use a combination of straight lines, arcs, flat surfaces, cylindrical surfaces and spherical surfaces.

To learn about creating high quality models of “smooth” surfaces start with an object with such surfaces.

Descriptions of continuity levels:

Yes, (As I understand this), it’s apparent in the the two horizontal polycurves used to create the upper band. Each has an arc with line extensions to meet at the quadrants of the verticals/arcs of either side. [quote=“davidcockey, post:18, topic:28619”]
Forcing a higher level on continuity such as G2 between such curves and surfaces generally results in regions with higher curvature near the transitions

This is a welcome bit of info as it explains the strangeness I often get after matching a surface. (Again, as I understand at this point)


Anyway, thanks for your generous help and patience and have a great weekend!


btw - if you’ve any links to modeling tasks that you find useful in this regard I’d be grateful to follow them up.

yeah, i see what the complications are… the examples i posted earlier are made with your same exact dimensions.