Surface flow – why it matters

Often when someone new to 3D shows their first model online, the form lacks definition and the whole thing looks a bit play-doughy.  And if they show the model wireframe, you can see the construction may have lots of polygons but the distribution is not even nor does it flow with the shape.  It’s often because they construct the model without changing surface flow.
Surface flow is directed with either the edges between the polygons or by polygons themselves – the same thing really.  It is usually called edgeflow.

Benefits of good edgeflow

  • more definition with less polygons, an optimized mesh
  • better deformation in animation (if built with anatomy in mind)
  • better shading

surf.flow good flows

I’ve prepared some examples, an organic shape done in two ways:
1.  with edges directing the flow
2.  no flow directions made

First image is our example shape, a cute  nose.

surf.flow nosepolys

Here it is as a basemesh and same with subdivision(control cage showing).  The nose has 42 polygons.  Now lets try achieve same shape and definition without any  flow direction – starting with 42 polys.

no surface flow, examples

As you can see, results don’t get much better with more polygons, somewhat worse in fact.  The model becomes difficult to work with.  Yet I’d still have to increase polycount to achieve the same definition we get with directed surface flow.  You CAN get good results this way in a sculpting program, working with thousands or millions polygons, but to get anything out that you can use in any other program, or animate for that matter,  you have to reconstruct the model surface flow.

surf.flow mouth exampleAnimated models benefit from good surface flow when flow is correct in places where the deformation happens, like around the mouth.  See the pic.  And sorry but I shan’t torture myself by building a poor mesh for comparison.  Just imagine a  rough head shaped tube here with a polygon or few pulled in for the mouth.  If you think that’s bad, imagine what happens when it is animated.

Good surface flow also improves shading simply because having a flow that defines the shape nicely from the ground up, you have every big and small part of said mesh aligned along the shape and not against it.  Also with good flow you do not have mesh issues(poles, etc.). When virtual light rays hit those parts, they reflect and refract as they should.  Shading, that is highlights and shadows and all, looks like it should.  I have no solid proof on this, but can say from experience that models with good edgeflow render better.

To conclude building without edgeflow is harder, needs more polygons and renders worse. Our nose is not the best example, but the difference should be apparent in the render below. Left nose is with good edgeflow, right is without.

comparing model with good surface-flow and other without

Besides the bit about animation, all of the above also applies to hard surfaces models, not just character models.  So model with directed flows, model well.  We’ll go into edgeloops and modeling for animation later.

This whole article, the concept, is one of those things I wish somebody had explained to me a long long time ago.  So here it is, in my words.  I hope somebody out there benefits from it.  If you found the article useful, or if you think it’s all nonsense, please comment – let me know.

22 Replies to “Surface flow – why it matters”

  1. Wow great write up! +1 🙂

    I am also new to modelling, 3weeks in fact, i believe to be good at modelling i should first get the fundamentals down first, as like you said in your blog its easier to get a good mesh first to work with.

    i found your write up interesting and have seen how edge flow is very important in other tuts and write ups around the web, if you want to add me to gmail or whatever go ahead :),

    And thanks for the nice blog 🙂

    1. Thank you Richard, very good to hear.
      Yes, I think fundamentals are good to work on early, but don’t let them stop you from creating models. I’ve seen some people get discouraged by the effort required for learning edgeflow and stop developing their 3D skills.. even though they definitely have the ability to learn and can put out quality in every other aspect. Edgeflow comes with practise.

      If you want an easy way to follow the blog developments, hit the “Subscribe by email”-link at the page top. That will inform you every time I post a new article. Subscribing to RSS-feed is the second way.

      Keep on modeling!

  2. Niko-

    Please never think that what you’re contributing to this art form is not needed.

    There are a ton of us late bloomers that like what you’re doing. It explains a lot in which I question as I am learning this new approach regarding my character art skills.

    So bring us more we are here reading and learning so much from you.

    This site of yours is what I have been looking for a long time because I think we all feel the same and very passionate about learning all there is to know about 3D.

    Savnac

  3. So regarding good surface flow, one needs to edge model to the contours of the design as clean and simple as possible, right.

    Or is there more to it.

    1. You said it well, Savnac. Model edgeflows to contours of the design and keep it simple.

      There is a bit more to it if modeling characters for animation and that is to model for countours and model for animation, both. Quite often modeling to design countours and making animation-good flows are the same thing, but in some places you need to choose which one you favor. I pretty much always favour animation and if I lose countours doing so I will find some other way (displacement, normal-maps) to bring them in.

  4. Dude, I most say ur the man. I been looking for this for so long, cracking my head looking for a correct mesh example to work with. I did a few models and my teacher corrected me, because, they lack of correct edge flow for animation.
    Thank you very much, I think your the only guy in the web giving free lessons on this. Thank you very much!

  5. Hi Niko,
    I see you are doing some really great work out of passion. I am really interested in doing small 3D movies. Just out of curiosity. I am zero in animation knowledge. Can you suggest me some softwares and some reading materials to begin with. Keep your good work going. All the best.

    1. Hi Vinodh,
      and thanks for the feedback.
      About software.. I have written a blogpost that lists some options. See here: http://www.cgmascot.com/production/animation-budget-tips/ If you’re all new to 3D animation I would suggest you try Blender – it offers a lot at costs nothing. Having started with something else it is harder to get into Blender because the interface is different, but starting from nothing it may be easier.

      In the end all depends on what you want you movies to have and at what budget and timeframe – your list of software needed and things you need to learn may be long or short. I suggest you keep things simple and don’t go for the most expensive can-do-all softwares at first(unless money is no object). Using smaller specialized software you can get by with smaller budget and build on it as you go forward. The techniques do generally transfer between software so learning one will help you a lot in another.

      Finally here is one list of 3D software’s compared. http://wiki.cgsociety.org/index.php/Comparison_of_3d_tools It is not complete but gives a good idea about features and prices, in general.

      For books I suggest you start with The Animators Survival Kit by Richard Williams and Character Animation Crash Course by Eric Goldberg.

  6. Hey Niko, am a newbie starting out animation and currently learning modeling. Thanx for this post, really helpful. 🙂

  7. You told me to comment, so here I am commenting. 😀

    To me this sounded like some very good info. Thank you for taking the time to write the article!

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