CAD models I would like to retopologize

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This discussion was created from comments split from: Seeking a more efficient retopology workflow.

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  • Ingsoc75
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    Ingsoc75 polycounter lvl 3
    I've got some CAD models that I would like to retopologize in Maya using Quad Draw. Do people use Quad draw for hard surface stuff (all the tutorials seem to be for character/organic models)?
  • perna
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    perna sublime tool
    @Ingsoc75 , retopo is unusual for hard surface. That's the beauty of a clean blockout mesh - you get the hipoly and lowpoly virtually for free.
  • Ingsoc75
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    Ingsoc75 polycounter lvl 3
    perna said:
    @Ingsoc75 , retopo is unusual for hard surface. That's the beauty of a clean blockout mesh - you get the hipoly and lowpoly virtually for free.
    What if your CAD model is a mess and needs to be redone?
  • musashidan
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    musashidan sublime tool
    Also, a lot of arch-vis artists are getting in on the real-time workflow and have no choice but to work with the CAD data they are handed. So it can often be an unavoidable necessity for some. It's actually a popular thread on the Max beta forums.

    @ingsoc75 As for quad draw, there's no reason why you can't use it. Just try it out and see for yourself. 
  • perna
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    perna sublime tool
    Ingsoc75 said:
    perna said:
    @Ingsoc75 , retopo is unusual for hard surface. That's the beauty of a clean blockout mesh - you get the hipoly and lowpoly virtually for free.
    What if your CAD model is a mess and needs to be redone?
    You could just keep it simple and use the CAD model as a 3d reference. Apply transparent materials and just build around it, with or without active projection. You'll have the option to permanently subdivide parts of the cage mesh to work in details. It shouldn't take too long considering it's basically connect-the-dots. I don't see much advantage to tools like quad-paint, which are geared more towards organic meshes.



  • Revel
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    Revel polycounter lvl 7
    @musashidan I think what the OP mean was he can spend more time adding more details to the sculpt (to looks pretty) more then placing proper loops/ manual retopo (to make them functional).

    I'm not a character artist but from what I see so far there is nothing beat the proper manual retopo work.
  • musashidan
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    musashidan sublime tool
    @perna but isn't this just essentially retopoing anyway? Although it' definitely more the go for organic surfaces, retopo toolsets in Max/Maya/etc are still using all the regular modelling tools so you can take advantage of set flow/relax/make planar/etc. This lends to making retop of hard-surface quite fast, I think.


    Also, just thought I'd mention the old Zbrush method of concept sculpting, retop with a very sparse density, and crease/subdivide. I used this very method last year on a project that I wanted to see if I could model a hard-surface character entirely in Zbrush. The process was actually quite fast. Although these are very simple parts, when resolving an entire character it is a lot faster for me to concept sculpt and iterate the design than modelling from scratch. Similar to a blockout. I suppose it just comes down to how our individual brains solve these puzzles. :) I still see trad sub-d as the predominant technique across the CG industry.

    Final character


  • musashidan
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    musashidan sublime tool
    Revel said:
    @musashidan I think what the OP mean was he can spend more time adding more details to the sculpt (to looks pretty) more then placing proper loops/ manual retopo (to make them functional).

    Yes, that's probably the case.

  • perna
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    perna sublime tool
    @musashidan , the intent is retopo, but the tools standard subdivision modeling. I only said that about snaps to make it sound more on-topic. I'd rarely snap, to ensure everything's planar when it should be, and the curve geo is so low-poly that snapping wouldn't give the correct results anyway.

    I'm giving more attention to hard-surface CAD retopo, with a lot of custom plugins and the like, but the workflow of starting with a clean block is still quicker on my end.

    For concepting I prefer to sculpt and the like, though I don't do a great deal of that.
  • Ingsoc75
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    Ingsoc75 polycounter lvl 3
    perna said:
    Ingsoc75 said:
    perna said:
    @Ingsoc75 , retopo is unusual for hard surface. That's the beauty of a clean blockout mesh - you get the hipoly and lowpoly virtually for free.
    What if your CAD model is a mess and needs to be redone?
    You could just keep it simple and use the CAD model as a 3d reference. Apply transparent materials and just build around it, with or without active projection. You'll have the option to permanently subdivide parts of the cage mesh to work in details. It shouldn't take too long considering it's basically connect-the-dots. I don't see much advantage to tools like quad-paint, which are geared more towards organic meshes.



    A very insightful way to handle CAD models. You would then take this simple blockout and add more detail to it?
  • Ingsoc75
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    Ingsoc75 polycounter lvl 3
    Also, a lot of arch-vis artists are getting in on the real-time workflow and have no choice but to work with the CAD data they are handed. So it can often be an unavoidable necessity for some. It's actually a popular thread on the Max beta forums.
    You bring up my situation as well (we handle military stuff for training). In the past we would take CAD models, optimize them and then procedurally texture and render. Now we are doing stuff in Unity and our models have to have good topology for unwrapping and texturing. I got to admit it's a new process for me after 15 years of doing it the other way.
  • pior
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    pior ngon master
    To be fair, this past workflow you are describing (taking CAD models, optimizing them and texturing them with simple procedurals) seems quite robust to begin with. Why bother doing a "AAA game style" retopo, baking and texturing pass if it is not really required ? (of course you probably have very good reasons for it, but I thought I'd ask.)

    Also in this specific case maybe the resources could be shifted towards establishing strict guidelines for the CAD models themselves, so that they could be used directly in your Unity project with no need for bruteforce optimisation and no need for retopo either. Now I understand that outputting CAD models at low tesselation values can cause models to not be watertight. Maybe that's the issue ?

    Also regarding retopo in general : there is always the solution consisting of outsourcing the task to an external vendor altogether. Training people for retopo tasks is after all pretty straightforward since it is basically nothing more than a game of connect the dots. That's what the comic book industry does for flatting (that is to say : the mask creation pass happening after inking and before coloring, often taken care of by an uncredited artist/assistant).
  • Ingsoc75
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    Ingsoc75 polycounter lvl 3
    It's a new challenge for me and I don't mind learning it.

    If I can find a good workflow (like the ones that some of the posters have suggested) for taking messy CAD models and making a high resolution one with good topology that I can then make lower resolution ones than I think it will work out.
  • pior
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    pior ngon master
    "taking messy CAD models and making a high resolution one with good topology that I can then make lower resolution ones"

    At this point if you want precise advice about all this you will need to post practical examples of what you are trying to achieve, because this sentence doesn't make a lot of sense :)
  • perna
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    perna sublime tool
    Ingsoc75 said:
    perna said:
    Ingsoc75 said:
    perna said:
    @Ingsoc75 , retopo is unusual for hard surface. That's the beauty of a clean blockout mesh - you get the hipoly and lowpoly virtually for free.
    What if your CAD model is a mess and needs to be redone?
    You could just keep it simple and use the CAD model as a 3d reference. Apply transparent materials and just build around it, with or without active projection. You'll have the option to permanently subdivide parts of the cage mesh to work in details. It shouldn't take too long considering it's basically connect-the-dots. I don't see much advantage to tools like quad-paint, which are geared more towards organic meshes.



    A very insightful way to handle CAD models. You would then take this simple blockout and add more detail to it?

    @Ingsoc75, that's not a simple blockout but final hipoly wip. Only one part needed limited subdivision to deal with all the crazy intersecting geometry there, but the result is well suited for most purposes.

    Once you get to grips with subd modeling the slowest work, by far, is blockout, as that's where you interpret the concept, deal with 2D cheats, etc. If you already have a "perfect" 3d mesh, no matter how messy, most of that work has already been done for you so it all becomes much more straightforward.

    I finished the part (albeit mirrored) as a demonstration. Here's the cage along with final hipoly:



  • beefaroni
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    beefaroni interpolator
    If you would like to re-topologize cad meshes easily I think Moi3d would be a great choice.

    It has by far the best CAD > geo converter out there. It will spit out the model with a combination of N-Gons and Quads. You'll have to play with the settings to find something that works for your situation.

    My advice would be to play with the upper and lower limit in the export settings to avoid small fillets or bevels that have a ton of edges that you will ave to cleanup later. It has a few problems with rounded objects that intersect other vert organic rounded objects where the edges will not line up perfectly. It's not too hard to clean that up in Maya or whatever modelling package you're using though assume you enabled the weld verts or whatever option in the export settings.

    They have a fully featured trial so give it a try and see if it works for your needs
    http://moi3d.com/

    Here's a quick shot of the export interface from a youtube video. Although it doesn't show the quads + ngons option..





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