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unfortunately i only have the option to export stl from fea software. i need that info to rebuild the cad model. it's a hot shape to cold shape transformation. so that the deformed part is the shape you want under load.

i'd much rather have a step file exported from fea but i guess that's too hard for them to do for reasons which you guys touch on in this forum sometimes.

thanks for the link to the script. i will definitely check it out. all i really need is the point locations from the stl too. so it doesn't even have to be a mesh in my case. i just need to know where to move the airfoils to so that i can re-loft the part. oh the joys of life.

i guess i should also add the cg location and inertias are needed for various analysis tasks. one of the things i hate about rhino is there ridiculous reporting of them. they clearly have no idea what they are doing. autodesk inventor was the best i have seen at reporting them and displaying the cg. but that's expensive software. i'm retired now so can't pay an arm and a leg to lease software. especially when that's the only thing i would need from the software.

i had tried autodesk fusion when it came out but really didn't like the interface. i looked at the fact sheet for visualcad and it isn't saying that it reports inertia. it doesn't even seem to loft based on the spec sheet. so it may be too basic of a program, which is why there is no youtube videos about it.

so far maybe viacad is about the only option. i used turbocad ages ago. not really sure if it could do the missing things i would need or not. any suggestions welcome though.

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Try meshmixer. Import your stl into MM, then export to obj etc.

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Hi Anthony ...
I came from Autocad to Rhino and then discovered MoI3d some time ago. Now I do as much of my work as possible with MoI (it's a joy to work with) and switch to Rhino 5 for dimensions and rendering tools. This combo works well for me. I anticipate that when 'dimensions' are available in MoI that I will not use Rhino much at all and will not upgrade to Rhino 6.
For rendering I use Sim Lab Composer and Octane ... both of which can read .obj files created in MoI3d.
cheers,
eric

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thanks eric,

i sense you can feel my pain. i can't wait to switch as well. thanks for the workflow advice. much appreciated. i have an old license of keyshot and that has served me well. i tried simlab composer due to Pilou's posts. it's nice for rendering but doesn't do toon shading. at least the last time i tried it. so i have been sticking with keyshot. but at some point i'll have to find something new i imagine. i can't switch to any gpu based rendering software because i'm on a laptop with amd apu. the toon shading is nice because you can render a frame fast so it makes animations doable for me. but i'm pretty much done having to render anything so i'm not worried about that aspect of things. i was surprised how much of a computer load rendering is. i can do cfd and fea with no problem on the laptop but rendering takes forever. i spent some time with keyshot settings to be able to get a half decent render in a resonable amount of time.

thanks co3darts,

i will look into meshmixer. something that can smooth out an stl file and turn it into a step file might save me a lot of work. i wouldn't have to rebuild the model in cad.

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i had one thought too. the fea software i used to use gave inertial properties. the one i'm using now didn't the last time i checked. but they changed solvers. so i'll look again. i might be able to find them there. the only thing with fea mass properties is they are always a little off due to mesh error. so if i can find them in cad that would be ideal.

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meshmixer was interesting. i installed it. i could import the stl and export to obj. so i would be able to import that to moi and use as reference geometry?

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Hi Anthony, it depends on the particulars of the file, like is it made up of several hundred thousand little tiny polygons or just a few hundred?

In general objects made up of very high density little tiny facets are not suitable for direct use in CAD. You would need a reverse engineering workflow for something like that. Those are tools such as Geomagic Wrap that fit larger NURBS surfaces to dense triangle mesh data.

- Michael

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hi michael,

everything i have done up to now has been small models. i don't forsee ever doing a large model. i mostly just do tests of various blade models. i've started to look at a number of things trying to nail down all the various things someone would want to do with my code. but even still, it would be small models as far as i know.

i haven't done all that many tests because of how time consuming it is. at the moment i only have extremely small stl test case. the actual blade test i did awhile ago i can't seem to find. it probably became outdated with a code change and then i deleted it but not sure. once i get v4 i will try an actual test again. by then hopefully my code will stop changing. never seems to end though.

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Hi Anthony,

I had a similar problem dealing with various STL files back when I was making jewellery.
One of the work a rounds was to use 3d-Coat as it will import an STL & convert it into voxels.
Aside from the sculpting elements that I used within 3d-Coat, it also has retopo tools with OBJ export.

https://3dcoat.com/features/

I personally found 3d-Coat's UI easier to use & understand, more so than the UI within Zbrush...
...the 3DC trial was fully workable, allowing for various tests before committing funds...
...the cost of 3DC was quite affordable, just as with MoI.

At that time I was using both Rhino & MoI, because Rhino allowed & worked with both mesh objects & NURBS...
...I'd import the OBJ into Rhino, create some basic NURBS geometry around it, which I'd then simply copy & paste to complete within MoI.
(MoI being far easier to use than doing similar in Rhino)

So given it's been done correctly, you should then be able to utilise the retop OBJ as a basic reference when brought into MoI via Max's script..?
...I can't actually test this for you as I've no longer got a suitable computer to do it on.

HTH, Colin

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thanks colin,

don't worry about testing. i was just curious what other software people would recommend. i know viacad and rhino come up a lot. but i don't really like those. i'll check into 3dcoat. thanks for the tip

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I second 3DC. It's a great program but has a learning curve and may feel foreign for a while but for import export retopo work it's simple.

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hi,

so i looked into options some more and had a question. it looks like the 3d coat retop to the viacad subd to nurbs might be a simple way to get a cold shape fea model back to a nurbs model. so it would go stl to obj to nurbs. but i'm not sure what 3d coat version has the retopo. can you use the cheapest one for 3d printing. or do you need at least the hobby version or higher.

viacad has a lot of powerful features packed into a terrible interface. so i'm not too keen on getting viacad. so i may not even do this. but was curious about 3d coat. i watched some videos about the retopo and i think it would be easy and fast to do. the 3d coat website wasn't helpful in figuring out what each version does though.

note; i just recalled that didn't moi add obj to nurbs? is that going to be a v4 feature. if so then i wouldn't have to suffer with viacad.

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Hi Anthony,

re:
> note; i just recalled that didn't moi add obj to nurbs? is that going to be a v4 feature. if so then
> i wouldn't have to suffer with viacad.

There is a new feature for converting a sub-d obj file to NURBS, it's meant for processing a sub-d control cage.

- Michael

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Try out instant meshes I use ZBRUSH for this function and must say this for a freebie does a very good job.

https://github.com/wjakob/instant-meshes

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thanks for the tip. i'll take a look. the models will be pretty simple wing like shapes. so it's nothing fancy.

michael, if the stl file gets converted to obj. will moi then convert it to nurbs? i thought that's what i was reading on the forum in the past. now it seems like you are saying not to do this. so i'm confused

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an earlier post suggested meshmixer. however, i don't see that it really converts the stl to a quad mesh. it will save it as obj but it's still triangles. seems like i need auto retopo? i'm not at all familiar with this stuff. so sorry for the dumb questions

update; instant meshes doesn't import stl files

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Hi Anthony,

re:
> michael, if the stl file gets converted to obj. will moi then convert it to nurbs?

Well it will, but it won't work very well because a triangle mesh which is what you have from .stl format is a different kind of polygon structure than one that is set up for sub-d smoothing.

For example, a sub-d control mesh should be formed of nearly all quads and not be very dense.

It's not really just a matter of just converting from one file format to another, the structure of an .stl triangle mesh is not the same thing as a polygon mesh that is set up to do sub-d smoothing.

- Michael

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i thought the auto retopo will take the triangles and make a mostly quad mesh. that's what i would bring into moi to turn to nurbs patches.

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Hi Anthony, yes if you additionally do that then you should be able to get a conversion.

I was just going by what you wrote: "michael, if the stl file gets converted to obj." , I was taking that to mean just .stl triangles converted into .obj triangles.

But I'm still not entirely sure that this process will be suitable for your particular needs - auto retopo is not focused on accuracy really at all and isn't going to try and match a particular tolerance value. The processes that uses it are more oriented around just rendering and visual artwork, not on engineering.

- Michael

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thanks it's making more sense now. looking at prices and features of various products still. 3dcoat seems to be a lot cheaper than zbrush. i watched some viacad and 3dcoat videos. in the 3dcoat video i can see what you mean about tolerances not being that close. it seems like the main point of it is to shrink the mesh. i think in the viacad video he mentioned tolerances and did a check for max deviations. but that was to the already retopo model. which like you said is rough.

i'm not really sure what i would want at the moment. it's more academic. i was just trying to figure out a workflow i could recommend to prop design users.

the method i was going to do was just use the stl as a guide to move the airfoil sections then re-loft. i'd still need to import an stl file. but that could be done for free with meshmixer. it would just keep the original triangle mesh from what i saw. it just saves that as obj.

so i guess i'm considering two different workflows. i'm not sure which would work better. i'd have to create models, do fea, etc... so that's a ways off.

i'm also trying to find something for inertial properties still. ashlar-vellum looks ok but it's pretty expensive. based on acis kernel so they probably have to pay a large licensing fee. viacad is very powerful but i don't like what i've seen of the interface. i'm done with rhino. so still looking on that front. i'll still keep rhino v5 because all my work for prop design was done in it. but at least i won't have to use it anymore. other than to look at an old model if i need to. i found that the dimensions weren't transferring to moi, when working with a forum user here. a lot of my files have dimensions in them. i can live without the zebra plot. so not worried about that.

can't wait for v4. counting the months. so right now i'm looking at moi, 3dcoat, and something for mcad. stuck with old keyshot too. all my prop design stuff is in that and unfortunately i can't get the same results with simlab.

anthony

i had one thought on the tolerance issue. since the parts are pretty smooth wing shapes. i would imagine it wouldn't be too hard to change the triangle mesh to a quad mesh. but maybe i'm wrong. they aren't lumpy faces and things like that. they would start of as moi lofts. go to fea. i find the cold shape. which is a slightly distorted version of the blade. then unfortunately that comes out as a triangle surface mesh. but it's still not too different than what went in. mostly it's the meshing errors. i guess if you didn't have a high mesh density it could be a problem. also for composite shell models i wouldn't need the retopo at all. that could just be converted with meshmixer. so i don't know. i'll have to think about it.

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i used to use alibre way back in the day. i checked it out again and they have atom3d. that is their hobbyist package. it says it can do mechanical properties from a step file. that's what i need. it's not super cheap but it's the best option i've found so far. the interface looks a million times better than ashlar vellum or viacad.

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