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hammondchips

CAD to C4d

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Hi cafe

I have a question that hopefully won't get laughed off the forum....

 

A small bit of background - I use CAD software like SW / Fusion 360 to create and C4D for all the fun stuff afterwards rendering mostly with Octane.

I've found a really nice workflow getting CAD file from STEP through MOI into Quad OBJ's and into C4D. They render well and can be animated too.

 

What I'm struggling with is keeping the nice geometry that Moi produces when doing minor mesh modification in C4D. As soon as I bevel or u-l and drag some lines around the mesh starts to render erratically. I've tried Optimising, Aligning Normals etc in C4D and if anything that seems to make things worse. The phong tag is working as expected, but once 'broken' the surfaces seems to be ruined.

 

So my question(s)

1 - Is there a fundamental difference between the mesh generated and modelled in C4D compare with one imported from CAD?

2 - Is there a way to import the Quads OBJ and enable normal C4D poly editing without it screwing up the surfaces?

 

Any help very welcome. 

Thanks

Alex

 

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Hi Alex, welcome to the cafe.

 

Yes, there is fundamental difference to the models that CAD programs produce, and things modelled properly inside a 3D app by anyone who knows what they are doing.

 

CAD programs do not care about topology at all, hence the meshes we get from them are almost always absolutely appalling, full of triangles, shading artefacts and problem topology, and utterly unsuitable for further editing in Cinema, or for use with Cinema's polygon tools, which expect and work best with all-quad meshes and sensible edge flow. However the whole concept of edge flow is alien to CAD software, so it's always something of a struggle to output this sort of thing nicely. Mainly all we can do is rescue it later. 

 

What can we do ? Well, we could model it again in Cinema, we could retopologize a terrible model in C4D, we could completely finish the model in the CAD program that created it so that no more editing was necessary, or we could try and rescue the existing model, which usually turns out to be marginally more effort than starting again ! ;)

 

But it's not all bad news. There is the odd magic bullet that can help. Look up Instant meshes, which is a brilliant, free application that takes rubbish geometry such as CAD apps produce, and autotopologizes it for you into nice quads where you can control polycount and direct the edge flow. That can be a life-saver if you do a lot of this !

 

CBR

 

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  • CBR

    !

    Whoa, what a reply in a matter of minutes, Thank you for sharing your wisdom.

    I'm going to watch some youtube on C4D retopogizing and take a look at 'instant meshes'

     

    If an autotopologizing process is successful, should that mean editing, and smooth surfaces 'should' render correctly from C4D?

     

    Cheers

    Alex

     

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    54 minutes ago, hammondchips said:

    If an autotopologizing process is successful, should that mean editing, and smooth surfaces 'should' render correctly from C4D?

    Yes it does ! You might have to reapply a phong tag along the way, but that's all, and the new mesh should work with all the polygon and selection tools...

     

    CBR

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    @cerbera - Instant Meshes looks amazing (away from C4d for a few days, so can't test it out, but as someone whoe receives his fair share of crappy CAD models, it looks like it could be a real game changer... I know you are the Chief Constable of the Quad Police, so a recommendation carries a lot of weight!

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  • Hi @Cerbera and wider Cafe

     

    Initially have had very little luck with Instant Meshes. Loading in what 'appears' to be a pretty nice looking mesh exported from Moi3D and i'm missing surfaces and the alignment of the quads seems to be fairly chaotic?

    From the examples on the site, Instant Meshes seems more designed for organic models? Anyone had success retopologizing hard edged forms?

     

    First image is from Moi3D

    Second image resulting OBJ loaded into Instant Meshes

    Third is the auto mesh produced without any tweaking

     

    Any thoughts?

    Alex

     

    5ae9b75b0be59_Screenshot2018-05-0214_04_15.thumb.png.dd42c5fd7a80157e3af1fcc4af2258a5.png5ae9b6e0d9e58_Screenshot2018-05-0213_59_36.thumb.png.94187dc0701fb77a04daa7b6ebb64318.png5ae9b732185be_Screenshot2018-05-0214_03_36.thumb.png.23fd37a19ebd3049e24f67d87a7f68ab.png

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    Ah yes I perhaps should have said that IM was optimized for organic and character meshes. You may be asking IM to do the impossible there - it doesn't like meshes that aren't all one connected surface as far as I remember. In this case I think there would have to be some manual cleanup first to prepare it for IM, if IM was the solution at all...

     

    But, looking at your MOI wireframe, unless that is hiding a ton of ngons and triangles behind the scenes that model actually looks OK in terms of topology (except for the boole type cut-out bit) and might render OK as it is ? Or do you need to edit it further ?

     

    If you can upload the obj as it came from MOI I'll have a look for you and see what the best course of action might be...

     

    CBR

     

     

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  • Amazing. Thanks. 

    I’ve spent some hours working a bit harder with the poly tidy up in C4D and even managed to get subdivision working on the forms (which in my understanding is a good sign ??)

    Away from the screen today but if you are still willing I’ll send a file or two tomorrow to get your expert opinion!

    A

     

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  • Time slipped away, but if you are still willing @Cerbera attached is a test mesh exported from Moi.

     

    Attached is an FBX and an OBJ of the same. 

    I use FBX sometimes as i can't get OBJ to create separate parts.

     

    Any input welcome

    Cheers

    Alex

     

    https://www.dropbox.com/s/rma9pvxe2eieir5/Test for Cafe.fbx?dl=0

    https://www.dropbox.com/s/bnqi9mtu6kuymvb/Test for Cafe.obj?dl=0

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    Ok the fbx is good in that it preserves the separate parts, and once the bits arrive in Cinema they initially look quite nice, topology-wise. You shouldn't need to Instant meshes this - it will be easier to fix in Cinema. A lot of it has good even segmentation, and at first glance you'd think you'd got away with it. But you haven't, alas :) On closer inspection, we can see that whilst some bits have good segmentation they are joined to other bits that have none, most notably the caps, which seem to be ngons. There might be a setting in MOI that stops that happening (I don't have it so don't know), but until you find that option, the ngon caps are not connected at all to the segmented walls which explains why your bevels and subdivision won't work.

     

    Essentially the repair work here is limited to deleting the ngon bits and replacing the surfaces with new sections. In the case of all those caps you can use a disc primitive to replace them, then connect and delete that model into the original, and stitch'n'sew the edges. After this, things should work a lot more predictably.

     

    There are additional problem areas wherever a boole was used in MOI, just in one instance in this model. Again, you have unconnected surfaces there and mismatching topology, so best thing to do is create new topo to replace the broken bits that does match that it's joining to.

     

    Sorry it isn't better news... everything in that file is rescuable but a) it'll take a little time and b) you will need to know the modelling toolset pretty well.

     

    CBR

     

     

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  • Hi CBR

     

    Pleased that you've identified some of the same problem I had, makes me feel like I'm making progress in the world of poly modelling.

     

    There is an option to export from MOI with meshed caps, but that seems to cause even more problems. see image attached

     

    In the interest of this being a learning resource for anyone else, this link is worth a read from the Moi forum.

    http://moi3d.com/forum/lmessages.php?webtag=MOI&msg=3196.1

     

     

     

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    Yes it does look as though the help very much wants you to leave ngons on ! :/ No pic attached, but I can imagine :)

    In that thread the solution seems to be doing largely what I suggested, ie cutting in new edges to turn ngons into quads, then connecting them to the existing topo using tools like Stitch'nSow and weld.

     

    Let's take an example object from your scene - I chose obj 1.

     

    That comes in looking like this...

     

    5af22243a8f98_part1a.thumb.JPG.73caba2247dc7e948c6f14cf6890b1db.JPG

     

    We need to lose the ngons that are the top and bottom caps. They are intrinsically broken, so don't try and cut into them - rather you need to delete them, and then do close polygon hole to put them back, THEN cut up the geo. Here, I inner extruded once, then made a quad cap, which gives us this, perfect for rendering, but time consuming to make because of all the segmentation in the original.

     

    5af22241607d9_part1b.thumb.JPG.9bd9de38409d6faa09dfab623cf176cb.JPG

     

    In this case, better to just start again with an 8 sided disc object, make editable and melt into quads (as shown below), then extrude with caps to get the thickness. Place under SDS to get the same sort of quality as above, but in a 10th of the time because of the much fewer segments we have to fix to make the quad cap. What I modelled on the left, SDS result on the right...

     

    5af2223e6d606_part1c.thumb.JPG.14ecd3516e398e54ad38ed708546d40b.JPG

     

    I do appreciate that not everything else in that file is as simple as this, but a lot of it is, and now we know that we can't trust the ngons, you are in a good place to recreate / fix the other model parts. If you get stuck on the boolean one let me know, and I'll show you what I'd do with that...

     

    CBR

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