3D Modeling Standards: Ngons

by Michele Bousquet

Our posts here on the best 3D modeling practices for different industries have garnered a lot of comments and opinions. One common theme is the question of quads (4-sided polygons) vs. ngons (polygons with more than 4 sides).

We’ve heard from both customers and artists on this matter. Some customers tell us that they absolutely must have quads and triangles, while others don’t care if the model has ngons. Unfortunately, when an artist publishes a 3D model for sale, there’s no way to tell which customers are going to want it. This means the safest course of action, if you want maximum sales, is to make a 3D model with quads and triangles only.



Ngons (left) and quads (right)

When I’ve mentioned this before, I’ve gotten responses ranging from “Of course! I always use quads,” to a very strong reaction from artists that seem to take this as a personal affront. “How dare you tell me how to model!” they say. “I’ve been using ngons for years, and my clients never complain. I am good at what I do, and I am a professional. I am insulted that you would insinuate otherwise!”

First of all, let’s all calm down. No one is saying anyone is unprofessional or a lousy artist. All we’re saying is, if you want to sell more 3D models, use mostly quads plus a few triangles where necessary. If you’re fine with the sales you’ve been getting on your ngon models, then don’t change a thing.

For artists that do want to update their 3D models, we’ve prepared a couple of videos on how to detect and change ngons to quads and tris in 3ds Max and Maya. Both these packages have tools for easy detection, and even some degree of automation for the process.

Do you find these videos helpful? Do you plan to change your existing models to use quads and tris only?

13 Responses to “3D Modeling Standards: Ngons”

  1. Kupfer says:

    I think that every modeler should be a model because it is more convenient, many modelers models of their models in different ways and this is correct!

  2. Alex Kontz says:

    Ngons isn’t a problem for flat surfaces, while organic or curved surfaces should consist of quads (or tris) of course. This has relation to the polygon nature, polygons must be coplanar. Ngon can’t be planar on curved surface, but quads. Meantime use quads in flat surface mean waste polygons, and sometime a lot. So, standartize quads or ngons is same, as a question what is better: fruits or vegetables? Each good in its case.

    And asking vendors “Ngons and Sales” isn’t correct. What about sales, I’d ask “Price Undercutters and Sales – What Do You Think?” What about standards there?

  3. Sandu Bublic says:

    100% agree with Alex. You read the forums (most of them). You realize what are our biggest problems: stolen models, undercutters, tons of free models. Those are real problem for us, the vendors, and, by consequence, for you, the market.
    What about putting those subjects for an open discussion ?

  4. Wow, it looks so much easier to get rid of the Ngons in Max compared to Maya. I was thinking of learning Maya a bit better myself since it is so big in the industry (I am a Max user originally). Are you sure there isn’t an easier way than manually splitting polys? Max has a lot more options.

    Btw, for max users who use older version than 2010 the “select numeric” isn’t available straight out of the box. But you could get pretty much the same tools in older Max versions if you install Polyboost, a Commercial script which is what Autodesk has included in 2010 allthough with a new UI. I believe there are some free scripts out there as well for detecting non quads/ngons/tris and whatnot. Tip! Search on Scriptspot.com

    And Alex is right. Quads is mostly important for organic stuff, or models that needs to be deformed smoothly, but I think it can be important for rounded surfaces as well (like car bodies, planes etc)

  5. Krystian says:

    @ Alex Kontz
    Actually only triangles are always planar by definition. Everything else above 3 vertexes won’t be planar on a curved surface. The reason for having mostly 4 sided polygons is for smoothing or deformation purpose. So if You have static, hard surface model, it doesn’t matter what kind of ngons You have.
    Using quads in a flat surface isn’t a waste of polygons as well because every ngon is treated internally as a bunch of triangles.

  6. Michele Bousquet says:

    The subject of undercutters and stolen models has been discussed among artists vigorously on the forums. We are working on a solution for this, which will take some time to implement. We know you are concerned about this. We have heard you in the forums about this over and over again, and believe me when I say we have heard you. We are working on a plan to address this every day. In fact, the larger thumbnails is a step on the way to that solution.

  7. Leonard Teo says:

    I’d like to add some clarity in terms of the technology. I hear artists always flat out say that Quads are the best and you shouldn’t use anything else, without understanding the technical reasoning behind it. It actually depends on what your output is – real-time or pre-rendered.

    For real-time, triangulating everything is best practice. From a technical standpoint, triangles rasterize very quickly and it simplifies many things as engine programmers won’t have to worry about non-convex polys, self-intersecting polys, etc. Content loading, etc. is made much simpler with triangulated models. If your output is real-time, using triangles is easier (technically) and faster than dealing with quads/n-gons, which is why many game/real-time engines want triangulated models.

    For anything with subdivision surfaces, you need quads because it retains the ‘flow’ of a model. Simple test – try applying a catmull-clark subdivide on a triangulated cube vs a quad-faced cube and you’ll see what I mean. Modeling with quads also means that you can easily add/edit edge loops. Adding some triangles is not a huge issue but if you have many, or ngons, you’ll break the general flow of the model. That’s why you want quads.

    N-gons where N > 4, in general, should be avoided. Once your polys exceed 4 sides, your risk of getting non-convex or self-intersecting polygons increases. There is absolutely no need for N-gons, as you can break them down by retopologizing to quads or triangulation.

    For artist workflow, I recommend modeling with quads. If your output is to a game engine, triangulate before export, but keep the model as a quad-based model. Many game exporters/importers do the triangulation automatically.

    As a purchaser of Turbo Squid models, even for game assets, I recommend quads. It’s easy enough to triangulate the models for real-time output. If you need to make any edits, having a model as quads makes life much better. It’s actually annoying that many game assets that are available come pre-triangulated.

    My 2 cents….

    Leonard

  8. Alex Kontz says:

    Discussing about game models we shouldn’t forget, TS already standardize them as Game-Ready assets. That mean, a model marked with Game Ready badge, have quads, non-intersected faces etc. This is standard and it work fine for such kind of assets, and anyone can use it right now. But there are a lot of models not intended for game industry. They are hi-poly, detailed models, best for visualization, not for real-time engines. And in my opinion, trying to apply common real-time rules to all models is a mistake. To make a commercial or any other 3d animation you shouldn’t have quad-modeled objects only. There are no problem with ngons, if they look fine when rendered. Say, you need a moving tank in your videoclip, and what is different, if the tank will have ngon sides, not quads?

  9. I thought that since all game engines interprets the models as triangles anyway, that some time during the export/import process the model would be triangulated anyways, so there isn’t really any need to triangulate it “manually”. In fact in 3dsmax even editable poly objects still has triangles “under the hood”, and you can even edit the triangulation (the invisible line that divides a quad/ngon) directly in editable poly.

    I do believe that realtime or gameready models can be optimized more if you don’t keep everything in perfect loops/quads, but instead remove geometry that isn’t need for the silhoutte of the model. Normalmaps takes care of the details anyways. So I guess for realtime purposes the rule of using mostly quads doesn’t apply the same way it does for subdivision models.

  10. Michele Bousquet says:

    The game developers I’ve spoken to say their engines triangulate the model anyway, so if the model isn’t going to be animated, it doesn’t matter whether it’s made of quads or tris or ngons. Where it does matter is when the model is going to be deformed during animation, as with a character or animal, or sometimes even a lamp post or car. At that point, quads are essential, as the artist will animate within a major package and export to the game engine later. But you never know what a customer is going to want to animate; someone might want to deform that building or car or even that stapler you made. Since quads work for everything, it seems prudent to model with quads so you get maximum compatibility with as many industries as possible.

  11. Sandu Bublic says:

    @Michele: “In fact, the larger thumbnails is a step on the way to that solution.”
    I know it’s a bit off-topic, but, for Heaven’s sake, please, Michele, enlighten me, how adding larger thumbnails will stop the undercutters ? Maybe there’s an esoteric connection between the size of the thumbnail and the price of the model, which I seem to miss ?
    Thank you kindly for your time, and believe me, I’m very glad to know you have heard us on the forums.

  12. adamk says:

    I thought Ngons were a Max only thing. One of my Pro-E friends likes to call them “max BS”. Whatever you want to call it – floating verts are bad. Even max actually works in triangles, it just shows you the edges by default. If you go into the object properties and uncheck “Edges only” you can see the triangles.

    If you aren’t using any kind of mesh smoothing on your model, you can typically get away with Ngons. But if you want better control over the triangles, and smoothing – it is a better practice to use only quads.

    Again, this goes back to the last discussion. The pros can recognize an edge loop – and I’ll go for a clean edge loop over an Ngon any day. Period. With the professional designation and model standards in place, I wouldn’t have to waste my time digging through the models on TS to find the good ones. I might actually start buying assets again. But the reality is for most of the small stuff – we can build a model faster than find a decent one worth purchasing on TS.

  13. Michele Bousquet says:

    Sandu, as you know, we’ve been very concerned about undercutting too. The solution, unfortunately, isn’t simple. We can’t simply remove products that undercut certain artists just because they don’t like it (what if the low-price artist is simply experimenting with pricing?) and setting minimum pricing for categories isn’t simple either (what about a low-poly or toy version that is truly worth the low amount?). Despite the challenges, we’ve taken all artists’ ideas on how to deal with this from the forums and surveys, plus several ideas from brainstorming here at TurboSquid, and we’ve actually come up with what we believe is a good solution. Unfortunately, being such a complex problem, the solution takes some time to put in place. So even though we’ve been working on this for some time, we’re looking at implementing the first parts of it in January or February. I can give you more information on it then.

    While we were working out the steps toward implementing the solution, we realized we’d need hi-res thumbnails and a few other goodies to be in place first. So yes, there is a connection, not so much esoteric as unknown on your end. I ask you to bear with me for a few more months, and you will see what we’ve been working on.

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