PDA

View Full Version : Need advice on Modelling for 3D printing

Bernie2Strokes
05-22-2015, 03:38 PM
128343

Hi there! I'm a beginner on Lightwave and I'm trying to create some game coins for 3D printing. But the process ended up with lots of bad polygons the printer can't understand.

I rushed it and used a 2nd party modelling software to combine the numbers from Lightwave. The cylinder was made in Silo 3D.

I want to create a new coin solely in Lightwave now but how can I avoid making more bad polygons when I combine the numbers on to the cylinder? This coin is supposed to be two-sided.

Sensei
05-22-2015, 03:54 PM
Merge Points, then Unify Polys.
Check whether you have 1-2 point polygons, and delete.
Press + in Polygon Statistics and hit delete.

MarcusM
05-22-2015, 04:15 PM
Addendum for LW 11.6, from page 6:

spherical
05-22-2015, 06:59 PM
I assume by "combine" you are using Boolean operations with two models. The issue with that is that, if the meshes are dense enough, there will inevitably be situations where the positioning of the two models will cause a bad condition, as far as the Boolean function is concerned. The more dense the mesh, the higher probability of this occurring. These two models are triangulated and appear to not be one mesh at this stage. Doing Bool Ops with Quads lessens the probability of a bad situation occurring, as there will be roughly 25% fewer Edges to cause problems, as you'll see. Convert the Tris into Quads, if necessary, then work with it. Triangulate as a last step.

A point is dimensionless. An Edge has only one dimension. The Point can never be divided in two. The Edge can only be divided along its one dimension; you cannot make an Edge be half its thickness—because it has no thickness. If the cutter surface encounters either of these through an axis of a Point or an Edge that has no dimension, the operation will either not cut the polygon or delete it; leaving a bunch of overhanging or missing cruft polys that have to be manually modified through Point Welding and One-Point or Two-Point poly deletion in order to make a water-tight mesh that a slicer can understand. That, or the Bool Op will fail altogether.

In your Point Statistics panel there are :

Points on zero polys. They can safely be deleted, as they are not forming a surface.
Points on one poly. These are most likely vertices that are on polys that need to be welded to other nearby points in order for a poly to form.
Points on two polys. Can be some of the above or deleted if they do not add any information to the mesh shape. IOW, along an Edge that if the Point is deleted nothing changes, as it is left over from a Poly Reduction.

Those three need to be dealt with first, along with consulting the Poly Statistics. Not having that to see, it is difficult to advise, but the usual situations are:

Polys having two Points. These will be left over when Polys are deleted or reduced. Pretty much, depending upon the Point conditions, above, they can be deleted. Check before doing so.
Polys having three points. Here's where working in Quads has another benefit. Three-point Polys are all that should be in a Triangulated mesh. Polys having three points in a Quad mesh are ones that need attention. This makes identifying the problem areas easier. Sometimes, you have to add a Point to an Edge, either with "Add Points" on a selected poly or "Connect" on a selected Edge, in order to be able to weld it to a nearby vertex and close a hole.
Polys having more than four points can exist as N-Gons in a predominantly Quad mesh, but a Triangulated mesh should not have any. Use "Connect" to create an Edge between two selected Points until you get to all Quads or Tris. OR, you can just wait for the Triangulation Op later.

Also check Edges Statistics. In all cases, there should be Edges on two polys. No more, no less. They're Edges that have no dimension, other than length, that join two things that have two dimensions:

An Edge on one poly, will show as a 2-point Poly in the Poly Statistics or be on a Poly that has a Point on only one poly or be on an N-Gon poly that has a drilled hole like the "0". The latter is the only situation where an Edge on one poly is legal.
An Edge on more than two polys will likely be a sign of interior geometry, polys within the actual outer surface of the model, or will be a redundant poly that is 2-point.

In any case, always Merge Points after a Bool Op choosing Automatic first, unchecking Keep 1-Point Polygons. If I have a problem mesh, I'll then re-run Merge using Fixed, starting with a very small value depending upon the mesh density, to weld very nearby points that Automatic ignored. Check with a zoomed in view to see if the mesh is degraded too much and Undo back to an acceptable value of Point distance, then commence the manual fixing Op from there on.

Once that is all done, you should have a clean, water-tight model that is ready for Triangulation. Then all polys will have three points and most all points will be on three polys; with the exception of conditions where many Tris are joined by one Point, as in the situation of a pole of a sphere.

Slicers need models that are "Manifold"; having only one outside and one inside, with nothing inside. If there are intersecting, overlying, overlapping or missing polys, the slicer cannot correctly analyze and identify the surface and cut it up into layers to create a tool path that will reassemble the shape.

In a situation like this, however, I would suggest not doing a Bool Op with two models but create the number's outline on the coin with "Drill" or "Solid Drill" using "Stencil" or "Slice" mode. This will make new Edges on the coin surface that you then Smooth Shift their interior polys up. Far easier to repair any anomalies and extraneous geometry when it is 2D, then make it 3D. In order to get the domed upper surface of the letters onto the shifted stencil, which will have the contour of the coin, cut the top polys of the Smooth Shifted number and paste the top polys from the number model, then Merge Points.

Note that this all applies to LightWave's native Boolean tool. Various commercial plugins, like 3rd Powers Boolean Tool in LightWave and Mesh Fusion in Modo, can better handle Ops like these, creating geometry at surface intersections where needed; even with filleting.

I had a high density model that is 4 feet long, having points roughly 0.060" pitch distance on average, that I had to cut along its length to create top and bottom halves. What made it even more difficult was that it was a tapered compound curve that undulated in all three axes; much like a curved tentacle in a "?" shape. 4" x 6" oval cross section at the root, morphing and tapering to round at mid distance and tapering to a point at the tip. The Bool Op left a LOT of cruft along the cut edges that had to be fixed before using Thicken to create a hollow shape that would be printed to be used as molds into which carbon fiber would be formed. It took a LOOOONG time to go through a mesh that dense and locate all problem areas before going to the next step. Save early. Save often.

Bernie2Strokes
05-22-2015, 10:39 PM
Thanks for the tips. I was hoping to start over with a flat circle polygon. I need the practice with Lightwave's tools.

Then somehow I'd combine it with the initial flat text of '10' with the text tool.

From there I thought I'd extrude select areas to form the rim and the numbers. They don't need to have the same depth from the surface.

Then I'd extrude the outmost sides back down for some depth and mirror it to create a two-sided coin. Once it's a whole object I'd fix any n-gons. Does that sound feasible?

spherical
05-23-2015, 01:30 AM
Well, you certainly can start over using a different approach. It may yield better or equal results, and you'd learn the benefits/pitfalls of them, but I was attempting to offer a solution to the existing method.

Bernie2Strokes
05-23-2015, 02:35 AM
I'll try that out too. Thanks.

Bernie2Strokes
05-24-2015, 11:35 PM
128364

Okay. So I've started over because the first model was too busy for me keep track of extra points and polygons.

I drilled the flat polygon of the no. 1 on to the surface of a new cylinder. I looked up the Drill command options and it drew the shape in better than trying a Boolean operation.

First I extruding it with Extender Plus and pressing 'T". But I couldn't repeat the same results so I just used the normal Extrude command.

Instead of using the Mirror command I tried Clone and merged the overlapping points.

I think at this stage I should cut up the geometry around the number 1 before I eliminate the junk points and polygons.

gordonrobb
05-25-2015, 02:55 AM
For many printers (and you should check the one you are using), there is no need for the number and the coin to be on single object. As long as the number object intersects the coin object, you'll be ok. You just need to make sure that all of the polygons are 3 or 4 points. A simple triple of polygons >4 points should work on an object this uncomplicated. (Unless you plan to subdivide it, in which case you need to try to put better geometry in. But, the thing that will simply this process more than anything is not having the numbers be part of the coin. (all of this is based on the assumption you want the numbers extruded from the coin, rather than embossed into it.)

Bernie2Strokes
05-25-2015, 03:17 AM
I don't know how to fix the number 'zero' in Lightwave. It's filling up the inside space instead of being an oval with a gap inside.

Before I just exported the number '10' into Silo 3D and played with it there. But I want to now how to fix problems like this in Lightwave itself.

Bernie2Strokes
05-25-2015, 03:20 AM
For many printers (and you should check the one you are using), there is no need for the number and the coin to be on single object. As long as the number object intersects the coin object, you'll be ok. You just need to make sure that all of the polygons are 3 or 4 points. A simple triple of polygons >4 points should work on an object this uncomplicated. (Unless you plan to subdivide it, in which case you need to try to put better geometry in. But, the thing that will simply this process more than anything is not having the numbers be part of the coin. (all of this is based on the assumption you want the numbers extruded from the coin, rather than embossed into it.)

I saw that mentioned in a video. I don't know if I should try that because I need to make a whole set of coins of each value. I still don't if I should lay them out in Lightwave with an array or just duplicate them manually in the printer's own software.

spherical
05-25-2015, 03:47 AM
For many printers (and you should check the one you are using), there is no need for the number and the coin to be on single object.

Slight correction. It's the slicer, not the printer. Printers know only that which the slicer sends them; that being a G-Code file that a slicer generates. If a slicer understands multiple meshes (also called sub-meshes) then, yes, the two shapes do not have to be combined into one before slicing.

Even if a particular printer has a companion software that may or may not be specific/proprietary, it's still a slicer. It could be a Cartesian or a Delta printer or a laser. Makes no difference when you get down to it. The process is still essentially the same and many slicers that are not associated with any printer will be able to work with all of them.

spherical
05-25-2015, 03:53 AM
128364

Okay. So I've started over because the first model was too busy for me keep track of extra points and polygons.

I drilled the flat polygon of the no. 1 on to the surface of a new cylinder. I looked up the Drill command options and it drew the shape in better than trying a Boolean operation.

First I extruding it with Extender Plus and pressing 'T". But I couldn't repeat the same results so I just used the normal Extrude command.

Instead of using the Mirror command I tried Clone and merged the overlapping points.

I think at this stage I should cut up the geometry around the number 1 before I eliminate the junk points and polygons.

I'm not really grokking what you are trying to do, here. If you Drill the surface and get the outline of the number on it, select the number's polys and Smooth Shift.

128365
This is a single poly with a hole in the middle, emulating your "0" number character. Drilled into the top poly of the box using Stencil mode. Select the poly that forms the "0" and Smooth Shift it up.

Bernie2Strokes
05-25-2015, 04:13 AM
I'm not really grokking what you are trying to do, here. If you Drill the surface and get the outline of the number on it, select the number's polys and Smooth Shift.

128365
This is a single poly with a hole in the middle, emulating your "0" number character. Drilled into the top poly of the box using Stencil mode. Select the poly that forms the "0" and Smooth Shift it up.

I forgot to mention that I'm doing three different coins here. They have values of 1,5, & 10.

I followed an online video on using the Drill command and it used both Extender Plus followed by pressing 'T'. It also used Extrude. I don't see how the results are different from Smooth shift

Anyway, I'll try drilling a stencil into the number '0'.

spherical
05-25-2015, 04:17 AM
Anyway, I'll try drilling a stencil into the number '0'.

You're not "drilling a stencil into the number "0", you're drilling the "0" into the coin.

The "1", "5" and "10" are essentially irrelevant. You can use the text tool to create the numbers or import a font through EPS to get a poly that is shaped like the number you want. Use that poly to Drill.

Bernie2Strokes
05-25-2015, 04:48 AM
Okay, but does anybody know why the number 'zero' doesn't form properly? I've seen this flaw in other 3D softwares so I'm curious why nobody has tried to fix it.

MonroePoteet
05-25-2015, 08:45 AM
I think it has to do with the point order in the polygon formed by the Text tool. To make the zero closed, it re-uses a couple of the points. You might try using Knife (Shift-K) to cut the zero in half before doing the Drill.

mTp

gordonrobb
05-25-2015, 10:35 AM
I find the text tool does that with any number or letter with a whole in it. Select the poly that is covering the hole and delete it, works for me iirc.

And thanks for the clarification spherical. I've only ever built stuff for other people to print so didn't have that level of knowledge. I just knew that some of the things I did could have overlapping shells.

spherical
05-25-2015, 07:05 PM
Okay, but does anybody know why the number 'zero' doesn't form properly? I've seen this flaw in other 3D softwares so I'm curious why nobody has tried to fix it.

Using the Text Tool or importing EPS? If importing, there is a checkbox to "auto-drill" the interior holes in letters/numbers/whatever. Otherwise, what gordonrobb said.

Bernie2Strokes
05-25-2015, 08:54 PM
Okay. New problem. All the numbers on my coins have come out reversed in STL format. I've opened up them up in the printer's software and in Silo 3D. They show the same problem.

What can I do to fix it? I made the numbers using the Drill method on to the surface of the coin and raised them by either extruding or smooth shifting. Did that alter the direction the polygons were facing?

128370

Sensei
05-25-2015, 09:39 PM
You can try using Scale -1,1,1 (instead of 1,1,1)
but this will flip normals.
Then enable double sided.

Bernie2Strokes
05-25-2015, 09:43 PM
Do you mean Scale in Lightwave or in the 3D printer program?

BTW: the models are already double-sided with the numbers.

Sensei
05-25-2015, 09:52 PM
In LightWave.

But I forgot that you have to print it..

So check whether Scale item works, if yes, then you will need to save LWO and flip in x in Modeler,
or set up nodes (Displacement) to do flipping in Layout..
then save transformed.

Bernie2Strokes
05-25-2015, 10:23 PM
In LightWave.

But I forgot that you have to print it..

So check whether Scale item works, if yes, then you will need to save LWO and flip in x in Modeler,
or set up nodes (Displacement) to do flipping in Layout..
then save transformed.

You've lost me there. Are you saying I need to go back to before I drilled the numbers on to the surface of the coin? Then I should Flip the polygons, drill them on the coin, then extrude them?

Sensei
05-25-2015, 10:31 PM
You've lost me there. Are you saying I need to go back to before I drilled the numbers on to the surface of the coin? Then I should Flip the polygons, drill them on the coin, then extrude them?

I made video tutorial for you:

Sensei
05-25-2015, 10:34 PM
There is also Modeler's Flip It.
And Scale -1,1,1 in Layout and Save Transformed Object.
Plentiful ways to fix digits on coins.

Bernie2Strokes
05-26-2015, 02:21 AM
Okay. So far that approach has worked. I've saved a new coin in OBJ format and opened it up Silo 3D. So far it looks good. So I'll try exporting it as an STL in Silo because doing it in Lightwave ends up making the coin flat. Thanks.

spherical
05-26-2015, 04:04 AM
Okay. So far that approach has worked. I've saved a new coin in OBJ format and opened it up Silo 3D. So far it looks good. So I'll try exporting it as an STL in Silo because doing it in Lightwave ends up making the coin flat. Thanks.

Sorry. From what I'm reading, none of this makes any sense. Convertng to STL would never invert/flip/reverse anything. Either it looks correct in LightWave at the end of the operation, or it doesn't. And "making the coin flat" really needs to be more fully and better described; because... huh?

Bernie2Strokes
05-26-2015, 04:54 AM
Sorry. From what I'm reading, none of this makes any sense. Convertng to STL would never invert/flip/reverse anything. Either it looks correct in LightWave at the end of the operation, or it doesn't. And "making the coin flat" really needs to be more fully and better described; because... huh?

I don't understand it myself. So far the only software that doesn't show that problem is the native Lightwave program. The 3D printer's software and my Silo 3D program showed the coins with the numbers facing in reverse. The normals appear to be facing outward properly, for OBJ and STL versions.

I've converted the lastest trial using Sensei's tips and it still suffers the same problem when exported in STL. I have to wait until tomorrow morning to see how the printer views the file.

Bernie2Strokes
05-26-2015, 04:57 AM
I get the feeling I'll need to print these out in OBJ format for now. Unless somebody can make sense of this I can't waste more time fixing it for STL output.

Sensei
05-26-2015, 10:19 AM
Disable Double Sided. In Modeler select wrong facing polygons and hit Flip 'f' key.

JoePoe
05-26-2015, 04:47 PM
Is your model really okay in LW? Have you looked at both sides in the 3D viewport?

I suspect you have stenciled all the way through your coin. One side would be correct and one would be backwards.
You would not see anything wrong while working in side and top wire views only (or whatever the right-reading axis is).
(edit: well you would see something wrong but might think everything was okay because of a "clean looking" number... which isn't right)

The model is coming in upside down is your other software and you're seeing the other side for the first time there.

Stencil one face at a time from the appropriate directions. Or Boolean or whatever, they all should work.

..... just my guess. :)

OR

If you're modeling one half and then duplicating it for the other side, whatever that operation is isn't right.
For example a simple mirror won't work, but a copy rotate paste will.

spherical
05-26-2015, 07:06 PM
Yes. That's why I said:

This is a single poly with a hole in the middle, emulating your "0" number character. Drilled into the top poly of the box using Stencil mode.

If you do not select a poly or polys, the Drill goes into all polys in its path axis; top and bottom. To limit how far it goes, make a selection and the tool works only on that.

EDIT: Thinking about this a bit further, there may be something Borked in the model that confuses the translator and slicer. Models need to be clean; squeaky clean.

I'd like to see the models you are working with, because there just isn't, in my experience, any way that converting from LWO to STL will alter the model's shape, such that it, or portions of it, are then backwards.

Either that, or we are all talking about different things.