Hi Elrick, yes probably Andrei's lofting method is what you'd want to look into.

But the whole area of "reverse engineering" where you're trying to reconstruct an existing shape accurately has a lot of complexity around it and it's not an area of work that MoI is really specifically focused on. So just keep in mind that it's a pretty advanced and tricky type of work that you're getting into here.

You'll generally want to make one single loft to be a broad and smoothly shaped surface, the other details like the sharp ridges and indentations will probably need to be trimmed out areas in the main hull where you have other smaller surfaces coming up from those trimmed areas, rather than trying to directly include those into one single loft.

> But by the looks of it only the most advanced and expensive mesh software can convert an Stl to an
> Iges accurately. GMD have a command to convert a polygon mesh to a solid (Iges) but the detail of
> the sharper edges are lost in the conversion.

Yes, polygon mesh data and CAD solids data are pretty different in structure. You can convert from CAD solids into meshes in a fairly straightforward way by dicing big smooth surface patches up into little facets but it's a quite complex process to go the reverse way and try to reconstruct large smooth surface patches from a big soup of little facet pieces.

There are various reverse engineering tools that are focused on that kind of stuff but they tend to be expensive and used for more special situations, not really part of the sort of "standard" CAD modeling toolset.

- Michael

Thanks for the advice gents!

> So just keep in mind that it's a pretty advanced and tricky type of work that you're getting into here.

This was my expectation.

I cant stray too far from the original designs because the bottom of the hull was specifically designed for high speeds on water. As were the pontoons. My main goal at the moment is to make a better 3d Pdf for online presentational purposes. I will attach a screenshot from a recent pdf I've made. The area I need to improve is marked. Because of its complexity I had to use multiple lofts. Its not very clear yet but Im starting to see the way in MoI. Do you think I might be able to use a network in the shape of this complex form and trim it away from a full loft? Or will I have a better chance to make solids and boolean subtract ?

Thanks,
Elrick

Hi Elrick,

> Do you think I might be able to use a network in the shape of this complex form and trim it away from a full loft?

Possibly Network or Sweep for the long ridge-like type pieces.



> Or will I have a better chance to make solids and boolean subtract ?

You'd probably want to work with Edit > Trim - working with solids and doing booleans can be convenient when you are able to use them but with something like a complex hull surface it may not be so easy to get it into a solid right off the bat. When that's the case you can use the Edit > Trim command instead of booleans.

Trim is sort of a "low level" way to do surface cutting - it allows you to cut a surface but then you manually pick which pieces of the cut up surface to discard.

Booleans are sort of a wrapper around Trim that automatically picks which pieces to discard based on which solid volume they are contained inside of. But if you're working with complex surfaces that are not so easy to maintain as solids then you'll probably be working more at the Trim level instead.

- Michael

Hi Michael,

Thank you for the advice! Im still busy thinking this through. There is on thing I noticed today which will be of enormous help to me. The shell command of GMD let me down on many ocations before and I saw the shell command from MoI does it very fast and trouble free! Making these parts hollow has been a pita.

I could add that section in the right marked area if anyone wants to try it in MoI. I''l be working on both MoI during working hours and GMD in after hours. I have to see if the rules in MoI have the same effect in GMD. But so far the spline by control points helped me smooth out all the waves in the contour lines I got from slicing the fuselage. Which would serve much better guide curves for the lofts.

I have one question I havent noticed in the MoI guide so far. Its a very simple thing I cant seem to do. Why is the splines in MoI stretching in a symetrical way when I try to move it? Which shortcut or button controls this?

Thanks,

Elrick

Hi Elrick,

> Why is the splines in MoI stretching in a symetrical way when I try to move
> it? Which shortcut or button controls this?

It sounds like it's the "History" function at work - after you do a mirror of something if you then edit the original the mirror transform will be reapplied and the mirrored version will update.

If you don't want it to happen you can disable history on that object by selecting the mirrored piece (or just select both pieces), and then run the Edit > History command and push the "Disable update" button that shows up in the command options area.

- Michael

Elrick,

I'm curious to know how you got the model from MeshMixer into MOI.

Mike

Hi Mike,

I exported the Stl from GMD into MM. After I've transformed all the lofts into one body and smoothed it where I can, I exported the stl back to GMD and used the "convert mesh to solid" comand. Its new features recently added to GMD. It makes Nurb surfaces from an existing mesh. Where the stl of about 1Gb shrinks down to 10Mb! It is effective but not a sound feature yet. The edges loses its sharpness. So if the shape contains sharp edges it might not be a good idea if you are looking for an accurate conversion. Only software I heard of that seems capable of handling this complex sort of calculations is Geomagic Studio & Design X. The trail versions wont let you export anything so I dont know how effective it is. Our project is innovative so theres no budget for such software yet. After GMD did the conversion I exported it as an Iges.

Will add some demonstrations. Its very useful to inspect surfaces in software like keyshot. Dont know if theres such but Im bussy looking for a Zebra HDRI? I dont like the zebra rendering from Rhino too much.

I were impressed to see how much the lofts have improved in GMD using Andrei's shared tips! After I saw the great results I got determined to redo this whole body. After this is done I will attempt it in MoI and give some feedback :)

Elrick

Sorry, what is GMD ?

GMD short for Geomagic Design. Others refer to it as GM. Used to be Alibre until 3ds baught them out. Not 100% sure about all the "politics".

Hello,

Using Blends and Fillets allows you to preserve some continuity between your surfaces and may end up simplifying them so you can tweak them a bit more easily. You might want to check out VSR/Autodesk tools for Rhino, and TSplines may be a candidate as well for this sort of surfacing work.

Thank you, Elrick.

When I checked the GMD website and looked for the price I only saw an email link, "Click here for a quote." Ugh, never a good sign for us hobbyists.

http://www.alibre.com/products/ad_compare.asp

around 2000$, 2000€, 1700£

Pleasure Mike! If your file arent too big I could try the conversion for you?

GMD's full package is quite expensive. But compared to Solid Works it aint too bad. I would have prefered to start this project in SW but yet again the budget. SW comes as one package I assume? GMD have quite some additional/optional software add ons. Choosing a package for your needs, keeping the prices low. The full package we got about three years ago included Alibre CAM (which I use quite often on the CNC machine), Keyshot (low resolution) and MoI. Some very usefull functions are the assemblies, configurations and constraints. When you, for instance, want to see all the doors open or wheels out, you just activate a configuration. (Havent noticed this in MoI yet?) Works with other stuff like colours, transparency and exploded views too. But I would say GMD is more on the mechanical side of the CAD world. On their forum there havent been much support for these odd lofts.

Theres one other thing I tried but didnt work so well. Exporting slices from Mesh Mixer to Rhino as obj's. Tried both "Stacked" and "Stacked 3d". Then use Rhino's mesh2NURB command, which were very effective on the slices, and export it as an Iges. Not a very practcal way because this takes forever. Probably depends on the size of your mesh and the software youre trying to import to. The mesh of this fuselage I is about 8,4m long 2,4m high 1,7m wide. With a cell size of 0.5mm containing 2.6 milion vertices. So I probably were pushing my luck. When I tried to convert the full body/obj Rhino kept on crashing. If you have rhino you could try a whole body. But in fact this doesnt give you Nurbs. Sort of an exact nurb replica of the mesh. See attachment. This small part took about 20minutes to load. Part 10 of 168. When the files started taking longer than 60 min I realised this aint practical.

Hi Elrick,

"My main goal at the moment is to make a better 3d Pdf for online presentational purposes." I also read that you have already have a mesh.

Is the existing mesh not sufficient to make a 3d pdf?

Hi Chris,

Thanks for bringing this up. Yes you can bring them into Pdf. But in my opinion, the renders from the converted mesh looks bad in Adobe. And to make this hollow will make it look even worse. So that option is out for this purpose unfortunately. Cos it was an approach I hope would have worked!

Forgot to mention that I also need to make keyshot renders. (Lovely place to inspect surfaces! It shows you flaws you wont see anywhere else.) I am positive that the lofts from MoI would make very good surfaces to render in KS. Thats why Im here :) But after Michael s heads up I realized this wont be happening over night. I should start with small steps to make sure how to utilize MoI properly. Will buy it for my own personal use to learn after hours.

Elrick













Some related shots about topics.

How was the mesh that you used in the 3d pdf originally created ... from 3d scan, output from other CAD software, or other?

I measured everything as the project progressed with self leveling cross lasers. We bought a scanner from nextengine to help us achieve something more accurate rather than this "ancient" method. But I quickly realized this scanner is not the hardware for the job. After numerous attempted fails the salesman came over to show me "how its done". And he got the same results. After working in NextEngines software, Scanstudio and RapidWorks, my curiosity started with mesh work. Thats when I started experimenting with Mesh Mixer. Really awesome software! The meshes I use in MM are Stls exported from the solids redrawn in GMD. The fuselage were done my the hands of our technical manager.









Top picture, original mesh exported from GMD. Didnt touch the export parameters. Bottom picture vertical beam and tape represents the planes (Z values). Made dots on the tape to find my X&Y values for the profiles. Used another laser square the vertcal beam. Simple method but open for many mistakes. (Tried to maintain .5mm accuracy)

So the mesh was not from a 3d scanner, but from 3d points measured using photogrammetry?

What are you using MeshMixer for?

There is software such as AGI's Photoscan that can create a mesh exclusively from photos (no laser needed), if you have enough suitable photos, and automatically construct the model. I am just starting to investigate this technique as an alternative to laser scanning.

I need to do some testing to determine what tolerances I could expect from a set of photos. There are a few variables that can impact the quality of the model.

I think I misunderstood after reading your reply again, it seems you measured the points manually on the tape and plotted them in a CAD program?

"The fuselage were done my the hands of our technical manager."

Do you mean that all the surfaces (and molds?) are made by hand?