Projecting curves technique

I’m using the project curves tool to create some transition surfaces but I’ve come to the fact that project is only in orthoganal directions and it seems I’ll have to create special c planes to get the job done unless there’s some better way.

Is there?

ProjectCurves.3dm (1002.9 KB)

ExtrudeCrv the curve in the desired direction using the Direction option so that it pass through the target surface.

Intersect the extrusion and the target surface.

Delete the extrusion.

I would over-build the radial surfaces downward and trim the bottom to the shape that includes those transitions.


To simplify my work I would just model the green section in my image below and then polar array.

No need for special C-Planes.

If you need to work with your model and the projection is the issue. Project in Front or Right, then rotate the model in Top view so you can project the “arms” that aren’t direct in your orthogonal views.

IHTH «Randy

That’s the simple answer I needed. :slight_smile:

That would be a fine thing, but unfortunately there are 4 different intersections and that technique doesn’t serve.

I have a trimming plane for the underside of the radials but it’s the rather amorphous shape of the transitions that’s giving me so much grief. I’m not sure how I’d make a cutting tool for the transitions you can see here. I’m going to look into perhaps cage editing a volume to get it.

Hi JK,

I made a very quick attempt with a simple approach, but I better ask if this is on the right track?


Edit: And this (with a flatter spoke) :

Start from a “Doughnut” placed between the two crossing rods, and then Curve \ Intersect to get the edge curves for the soldering on both rods. Then hide/delete the doughnut and run Sweep2 (closed). You can make the cross curves from extracted Isocurves :

The cross sections curves (yellow) for Sweep2 was made with BlendCrv starting from the extracted (red) isocurves shown in this picture (never mind the texture, something happened to the renderer and it went bananas):

// Rolf

That’s a good suggestion Rolf. I’ve been at it now all day and I’m still not finished. There’s aspects of Rhino I find to be utter bullshit. Problems arise and multiply when any form gains more than a modicom of complexity. Massive numbers of points are generated creating ridiculously heavy surfaces and curves. Rebuilding anything detaches it from any number of critical points that then must be manually reconnected and god help you if you forget any, then there’s another several steps to be taken to get back to where you wanted to be.

Man I’m disgusted with this application. It’s not the designing tool I expected. That is, I expected after over a year of dedicated study it’s still a tedious endeavor to get anything done. I spend way to much time meeting the applications needs and deffereing my own.

There you have a point. Not a Point, but a point.

I actually succeeded in making the “soldering” quite smooth (and joining with the bars/spokes), but I’m also trying (right now) to CP edit the “doughnut” (expanding it) as to “spread” out the soldering in the “corners” (the intersection curves) to get closer to the original geometry. I think Its possible, but I realize that it takes some experience to not get oneself into deep trouble…

Perhaps this kind of geometry is best achieved with T-Splines.

// Rolf

This is what I’m trying right now (ControlPoint Editing the “doughnut”:

The intent is to try to make the intersection so “smooth” that Sweep2 won’t make any creases. But if it still does, one can try inserting some extra cross guides (while in the command dialog) as to straighten out such troublesome places.

I continue to be made aware of the t-splines option that’s not an option for the mac version. So I’ll have to muddle along with rhino’s limitations. Getting a smooth transitioning surface that accomodates the surfaces is a major project for me.

The objects I need to deal with don’t lend themselves to easy solutions - at least as far as I can manage.

Take a look if you please. :slight_smile: (1.4 MB)

Ah, yes, you use the Mac version. Sorry, didn’t think of that.

I actually do not use T-splines myself (as I try to master Rhino first). So we’re in the same boat so far.

I’ll take a look at your model.

I want you to know that I find it very interesting to be able to solve these kind of problems, since I will soon be there myself (drawing an old car, with cast metal details which often look much like these geometries (hood hinges, chassi details etc).

Don’t give up! :slight_smile:

// Rolf

Hi James,
I’ve now tried to go about rather systematically, and using obvious “ridges” as starting points for BlendCrv’s as a basis for the “soldering” surface.

There was no chance to get the surface to not crease with only “vertical” BlendCrv network. So I tried adding Points on the middle of the vertical BlendCrvs and adding a “middle guide” curve as to force the soldering surface to stay up without creases (see middle curve in picture below). I used NetworkSrf for the surface in this picture.

But it wasn’t enough to only put this line in place. I also had to find out where / what exactly caused the creases. And this is how I did it.

  1. First I added the “middle curve” (curve though points) as mentioned above.
  2. Turned History ON.
  3. NetworkSrf
  4. Then I inspected the surface. Well, surprise, surprise, it still had creases.
  5. Back to work: SInce I had had History turned on, I could now drag and push the network curves (I ficused on the “middle curve”) trying to make the surface smooth out kindly. And gradually, after som jerking the surface was fairly smooth.
  6. Then I scrapped the surface, made the curves cross each other more exactly.
  7. NetworkSrf again. And that is what you see on the picture.

Have some more trixing to do until I get around the whole thing, but this looks very promising. No problem. Ahum. :slight_smile:

Edit: Ops, forgot to turn on the BlendCrv guides in the picture :

  • Cyan: Starting curves for BlendCrv
  • Red: BlendCrvs
  • Orange: Intersections

// Rolf

Hi again James,

Attached one soldering which perhaps would be good enough as a base for a rough texture. I didn’t find a very convenient way as of yet. For this one I used brute force (well, a bunch of BlendCrvs or course, but I still had to cut out some minor irregularities and patch them, and round of with a “pipe transition” along the upper edge. See pictures par below.

I also fixed the corners by extending the steel bars and making a “cut surface” in the corner. The cutter srf was made from Points placed so the cutting angle would be correct. Like so:

Fig 1. I made a cutting surface from three Points giving the right angle in this difficult corner (then I mirrored to the other corner, see fig 2.) :

Fig 2. The other corner :

Some images of the “soldering” :
Fig 3 Patched some irregularities :

Fig 4 : The result :

Fig 5 :

Fig 6 :

Fig 7 :

I don’t know if you have any use for it, but here’s the model. (I moved the item to the World center).

GratesPract 011 Final.3dm (6.6 MB)

// Rolf

Where you have Rolf’s example:

Try using the _SplitEdge command and then _BlendSrf with tangency or curvature


That’s beautiful work Rolf! I’ll be at it again today and hope to show some progress. I really appreciate your help.

James, it may be ok with texture, but it seems to take too much work. I’m trying to find a quicker way to get at it. I’m gradually learning why the thing causes creases, which also hints about how to approach it from start.

// Rolf

That’s the crux of my issues with the application. It seems over time there would be programming that would steadily reduce the need for such ‘work arounds’.

Indeed, AI is rapidly eliminating the need of human effort for growing number of cognitive tasks. And Design software like for instance Zbrush continues to make the translation of a designer talents to digitized results more ‘natural’. The necessity of accommodating the application is inversely proportional to it’s continued use.

Never mind

Ops, I had moved the whole thing, but had the construction lines hidden, so they were left hidden and out of place (saw that after I had posted). I’ll repost, hold on.

Edit: The updated file:

GratesPract 011 Final.3dm (6.8 MB)

Notice that I didn’t get a “clean result” directly even with these construction lines, only “close to”. Had to manually adjust the surface. Possibly the curves can be adjusted still (like another upper-middle horiz "line) but there must be a systematic approach which always works “according to theory”, otherwise it takes way too long.

The “tighter” side (outwards) works almost flawless, the inner fillet is… well, there must be an approach that works at first attempt. I’ll find it sooner or later.

Working on it.

// Rolf

The construction lines will not be very meaningful unless you study the picture below.

The “horizontal” construction lines are cut off so that one can start with a smaller patch (pictured) using NetworkSrf (tangency at top & bottom). See which exactly which curves to select for this first surface in the picture.

(I had to use a “pipe-cut fillet” on the upper edge, hence the narrow surface on top, plus a cut & patch on each side due to a small irregularity).

After the first patch, the rest of the surface can be made in one shot. All the other construction lines to be selected. Use NetworkSrf for both surfaces because of the horizontal lines, which Sweep2 won’t accept.

On the last big surface I used the first surface’s edges instead of the two vertical construction curves shown in the picture.

As mentioned earlier, I rounded off by cutting out the upper edge with a pipe and did a BlendSrf. That resulted om some small pieces as well (watch out when exploding) which I didn’t bother fixing.

Almost there, but only almost. So I’m looking for a more systematic and quicker way.

// Rolf