Edit Lion Head

[Henry_C_Millman]

This lion head was imported into Rhino as an .obj file mesh. I want to isolate the head from its backing and use only it in a new model. I was able to turn the mesh into a closed polysurface solid, but that is as far as I was able to get. All further attempts to separate the head from the background have been unsuccessful. How can this be accomplished? I need some assistance after trying for several hours. Thanks.

[martinsiegrist]

If the surface is somewhat oriented, you can go into a side view and trim it with a vertical curve or line…

Are you using Rhino 8?

[Normand (Jakob Normand)]

@Henry_C_Millman

I was able to turn the mesh into a closed polysurface solid

Hi @Henry_C_Millman
How? If done by using MeshToNURB or ToNURBS what you have now is a polysurface consisting of (potentially) a LOT of surfaces, and they can be hard to work with downstream. My best advice would be to first delete the part of the mesh you don’t need and then use QuadRemesh to create a SubD version of the head - and then convert that to NURBS. It’ll give you a more organic, smooth lions head and will be much easier to edit and use. If this doesn’t make sense, please post the file, as we can’t see the actual base mesh from the screenshot.
HTH, Jakob

[Henry_C_Millman]

Mr. Normand:

Thanks for your response.

I used MeshToNurbs.

I have attached the file that just has the mesh. I was unsuccessful at trying to figure out how to delete just a part of the mesh. How do you do that? Then I will try the rest of your process.

HAR 2364 Frederick Douglas Blvd 3D.3dm (9.3 MB)

[Henry_C_Millman]

Mr. Siegrist:

Thanks for your response. I understand your method and will try it.

[wim (Wim Dekeyser)]

Hi Henry -

@Henry_C_Millman

I was unsuccessful at trying to figure out how to delete just a part of the mesh. How do you do that?

You can use SelectionFilterFaces to make sure to only select faces of the mesh, and then simply window-select areas of the object. Then hit the Delete key. Make sure to turn off selection filters when done.
-wim

[Normand (Jakob Normand)]

@wim

You can use SelectionFilterFaces

Which again can be combined with SelBrush for a more freehand approach - but do note, that the underlying base mesh (left) is very coarse and quite unprecise compared to the look of the textured scan. That’s the downside of smartphone scans

HTH, Jakob

[Henry_C_Millman]

Thanks to everyone for your advice. I was able to remove all of the mesh except for the lion’s head. The next problem I have been unsuccessfully struggling with for quite a while is how to turn the open mesh into a closed poly surface so that it can be printed in 3D. I tried to trim the rough edges at the back of the head with a cutting plane, but that did not work on either a mesh or an open poly surface. I would be grateful for any ideas as to how the creation of a solid might be accomplished. Please let me know if I am trying to do the impossible and will have to sculpt this head from scratch to get a good 3D print. Incidentally, the original scan was done with a professional drone, not a smartphone.

[pascal (Pascal Golay)]

Hi Henry - this looks like a bit of work, to me - the rthing is a mesh and printing requires a mesh, so that part is fine. What do you envision the print to be - a closed solid - basically with a flat back,

or a constant thickness shell of the shape?
BTW, as is the object is very small in Rhino - you will want to scale it up.

-Pascal

[lander (CAD CAM CNC)]

@Henry_C_Millman

I was able to turn the mesh into a closed polysurface solid

I surmise the workflow you’re referring too, wasn’t the optimal approach.

@Normand

If done by using MeshToNURB or ToNURBS what you have now is a polysurface consisting of (potentially) a LOT of surfaces, and they can be hard to work with downstream.

Indeed.

@Normand

use QuadRemesh to create a SubD version of the head - and then convert that to NURBS. It’ll give you a more organic, smooth lions head and will be much easier to edit and use.

This is one of ‘my new fav’ ways to approach these scenarios. and maybe some shrinkwrap

@Henry_C_Millman

I need some assistance after trying for several hours.

Give it a couple weeks jk

@Henry_C_Millman

I was unsuccessful at trying to figure out how to delete just a part of the mesh. How do you do that?

There’s several methods at least. A fun one might be to turn the points on for the mesh and delete some to see what happens

@wim

You can use SelectionFilterFaces to make sure to only select faces of the mesh, and then simply window-select areas of the object. Then hit the Delete key. Make sure to turn off selection filters when done.

This one might be more fun though

@Normand

again can be combined with SelBrush for a more freehand approach

I’ve used that tool a few times, and it’s pretty cool. I’m still getting used to Rhino having these new cool tools. Well, some have been around a while, but I took forever to upgrade from V5 to V7 so

@Henry_C_Millman

I was able to remove all of the mesh except for the lion’s head.

nice

@Henry_C_Millman

how to turn the open mesh into a closed poly surface so that it can be printed in 3D.

Ah yes the proverbial solid mesh thing for printing

@Henry_C_Millman

the original scan was done with a professional drone

That’s cool!

@pascal

printing requires a mesh, so that part is fine. What do you envision the print to be - a closed solid - basically with a flat back,

or a constant thickness shell of the shape?

Indeed there’s nearly infinitely many ways to comprise these print compositions

Imma start doing some more prints and mesh work soon, and I’ll probably get back into the volumetric voronoi approach with GH

[Henry_C_Millman]

Mr. Golay:

Thank you for your response.

I am very new to all this and did not consider a constant thickness shell which could be attached to a flat backing surface. I will try that.

The other problem is the lack of detail, so I will have to do some work on the mesh to get the detail I want.

By the way, I did manage to create a closed solid polysurface but only with the help of a free trial of a very expensive add-on called Mesh2Surface. It is about $1,300.00 which I really cannot afford. (See attached screen shot)

Fortunately, this time-consuming work is all experimental for now with no fixed deadline.

[lander (CAD CAM CNC)]

@Henry_C_Millman

I did manage to create a closed solid polysurface but only with the help of a free trial of a very expensive add-on called Mesh2Surface. It is about $1,300.00 which I really cannot afford. (See attached screen shot)

That plugin is obsolete – imo. Save your money.

@Henry_C_Millman

Lion Head closed solid polysurface799×961 274 KB

You can obtain the same composition if not better, using Rhino’s new quad remesh and shrinkwrap stuff – in a timely manner for almost $0.

Instead of ‘meshtosurf’ there’s also rhino ‘resurf’ for probably alot less money, but they’re both basically obsolete at this point with Rhino’s new evolutionary features.

[davidcockey]

Why do you need a NURBS surface?

MeshToNURB should not be used to convert a high density mesh. MeshToNURB creates an individual NURBS surface for every mesh face. The result is usually not useful.

[Rhino_Bulgaria (Bobi)]

A single NURBS surface could be used to replace all the patches of the model shown above. A quick but coarse way to do that is to simply use the “Drape surface” tool. However, if quality is more important than time, then I recommend to manually sculpt a single NURBS surface by adjusting its control points.

[Henry_C_Millman]

Thanks to all for the many useful comments and advice. As a brand-new Rhino user, I intend to explore all of your suggestions and keep at it until I figure out a solution that works. In doing so, I am sure that I will learn a lot.

[lander (CAD CAM CNC)]

@Henry_C_Millman

Lion Head closed solid polysurface799×961 274 KB

@lander

Instead of ‘meshtosurf’ there’s also rhino ‘resurf’ for probably alot less money, but they’re both basically obsolete at this point with Rhino’s new evolutionary features.

Got hung up today with dayjob stuff…

At any rate,

Using this as reference, first step in my example workflow here is sketching poly line on mesh:

I tried meshsplit with that original polyline I made but wasn’t happy with the results, so I rebuilt the curve and faired it out a bit, then trying the ribbon command, still not happy with the results…

It’s like the crv normals are twisted or something… Rhino’s like “idk” haha

The ribbon would almost work and probably get me a better split, but this darn curve lol …

It would be cool if Rhino could use a mesh to calculate a curvature analysis and add a parting line…

Guess I’ll have to convert it to nurbs for that …

Almost got a usable cutting srf via srf patch…

Would have to modify the neck area…

Extruding straight almost provides a useable srf, but would need to taper it or something…

This might work:

Had to merge some srfs and use moveUVN to move the V’s inwards.

Yep that gave me a much better result for meshsplit:

Now I can focus more on the isolated area.

Welded the mesh, reduced by 5%, then quadremeshed w/ 5000 quad count 100% adaptive:

YOU COULD PROBABLY USE 10,000 FOR TIGHTER INTERPOLATION QUAD COUNT. AND SIMPLIFY IT LATER. OR ONCE THE FACE IS CUT AS INTENDED THEN THE REMESH CAN BE ISOLATED TO THE MESH AGAIN. IT ALL DEPENDS ON DESIGN INTENT.

@Henry_C_Millman

Lion Head closed solid polysurface799×961 274 KB

I then was trying to find a good parting line, but couldn’t find it in the curvature analysis GUI, so would probably have to add it manually like you did before.

HAR 2364 Frederick Douglas Blvd 3D_emod.3dm (9.4 MB)

[lander (CAD CAM CNC)]

@lander

I rebuilt the curve and faired it out a bit, then trying the ribbon command, still not happy with the results…

It’s like the crv normals are twisted or something… Rhino’s like “idk” haha

The ribbon would almost work and probably get me a better split, but this darn curve lol …

It would be cool if Rhino could use a mesh to calculate a curvature analysis and add a parting line…

Maybe this was my issue:

Ribbon and RibbonOffset - why two similar commands?

ribbon offset has a lot of stuff built into it… ribbon simply creates a surface extruded normal to a surface, ribbon offset makes a 3d curve and gives you options to create surfaces between your original curve and your projected curve. the intent of ribbon offset it to make a parting line surface for a mold. see video here- [Rhino 7- How to Make a Partition Surface]

I’ll need to try ‘ribbon offset’ and see if that was it…

It’s weird I can’t find any threads on this:

@lander

I then was trying to find a good parting line, but couldn’t find it in the curvature analysis GUI, so would probably have to add it manually like you did before.

ahh I had the wrong nomenclature:

Draft angle analysis unable to create draft curves

I just figured out that the “Draft angle analysis” tool is no longer allowing me to create draft curves. The “Create Draft Curves” button stays grey no matter which file I open. I also restarted my PC and it’s still that way. Is that a bug that has happened with the recent updates of Rhino 7? [Screen Shot 03-21-22 at 11.47 PM.PNG]

‘draft curves’

this is so cool, I’ll remember the command eventually

Ahh I need to remember ‘draft angle analysis’ too

Fun tool

Maybe there’s an easier way to do this, but I basically used draft analysis on the subd, and locked it’s layer with transparent rendering, then manually traced the mesh with poly line on mesh.

Then I’ll try using that to further simplify the mesh that’s used for calculations, and try ribbon offset again to trim it o’ course.

yeah just extruding it straight again or tapered might be the quickest

yeah basically using the previous workflow I did further above

just doing a more precise cut around the object of interest I think

some rebuilding smoothing extending etc.

that’s the best way to split imo:

The first time I ever did something like this I was a total Rhino newbie and spent two weeks setting it up (on a much more complicated part) – without even knowing it would work until the setup was done.

That’s how I knew this would work.

Now let’s see the new results:

more accurate version:

HAR 2364 Frederick Douglas Blvd 3D_emod.3dm (12.6 MB)

[Henry_C_Millman]

Many thanks again for the great comments and advice. I am a Rhino newbie and had no idea that this would be so seemingly complex to do. I really appreciate the detailed instructions and screen shots.

This lion head is a small free-form detail on a sheet-metal cornice, most of which is thankfully more geometric. This is the second cornice that I have tried to draw in Rhino. A perspective rendering of the first one I completed is attached.

CHT 30 E Bway cover 3d perspective.pdf (195.0 KB)

[Henry_C_Millman]

Attached is a screen shot of the first cornice I drew so you don’t have to download the previous post’s .pdf.

[lander (CAD CAM CNC)]

@Henry_C_Millman

had no idea that this would be so seemingly complex to do.

The idea is to come up with a workflow that streamlines the process to accommodate the ‘design intent’.

Technically this process of reverse engineering was much more complex before Rhino 7 ever existed.

Since Rhino 7 and 8 exist, this process is exceedingly less complex – depending on design intent.

If you need more accuracy than R7 or R8 can provide, then you’ll need a $70k 3D scanner and a $20k reverse engineering software program – then yes that’s complicated.

Now, if you can only scan the object with a LIDAR camera on a drone copter, then the accuracy wont be that great anyway, and therefore a $20k program wont make sense. So R7 or R8 is perfectly adequate with no additional plugins necessary – imo.

So then it’s a matter of tracing the mesh in Rhino and splitting it, and remeshing it into subd etc. – yeah maybe it still sounds complicated but the workflow can be distilled down into a specific recipe that should be very easy to follow – imo.