Do You Have to Model in Quads? Tris, Quads & Ngons Explained
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- Опубликовано: 29 июл 2024
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In this episode I talk about why it helps to model in quads and when using tris and ngons can be useful. I also talk a bit about topology and give examples of when the different methods can be used in both modelling and animation
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Under the hood, 3D renderers indeed normally store every mesh as triangles. That is because three vertices (like in a triangle) are always on a single mathematical plane, whereas a quad can be "bent" (the fourth vertex might not be on the same plane as the other three). That's for example why a four-legged chair may wobble, while you never have that problem with a three-legged chair.
If you take a normal quad plane in Blender and move one vertex up and down, you will see that it forms a sharp edge that visually seperates it into two triangles. I don't know about Blender, but 3DS Max even lets you manually change which diagonal is used as an edge for internal triangulation (it's rarely ever relevant, but it can improve corners/rounded parts on low poly models sometimes).
One technical example why renderers want triangles is because it lets them confirm whether the camera sees the front, back, or exact side of the triangle in a single calculation. If you see it from the side you have to discard it since it won't fill any pixels, and many render modes will also discard all triangles that you see from the backside. Whereas if you have a bent quad, you may see both front and backside at the same time.
And for raytracing, the planar nature of triangles means that the ray/triangle intersection calculation is a whole lot easier than that for rays and quads.
indeed :)
I believe the last time logical quads were used in a major 3D renderer was for the Sega Saturn, It was based on Sega's arcade technology of the time which was designed during the "wild west" days of 3D development. Apparently, this caused a lot of headaches for developers back in the day. As by the time the system was released Tris were the standard.
It is also because the triangle is the simplest shape that can represent a surface, they are atoms.
@@anselme198 Didn't get the atom part.
@@petarpetrov5548 The definition of a atom is something that is unreductible, unsplittable, it comes from the greek "atomos", that means "uncuttable". In that sense, using the philosophic meaning of atom, not the physics one, you can say that the triangle is the atom of a mesh.
Thank you for answering my biggest question. I've been nervouse about making game characters in blender due to not knowing how quads would act should they get a bit... bent up. But knowing that those get divided in to tris is reassuring that I can do what I need as long as I keep in mind that each quad is a double tri... which doesn't much matter in my case as I'm shooting for minimalism.
That was the best explanation of poles vs loops in retopology I’ve ever seen. Thank you 🙏
grant you are just absolutely awesome! hope you realize how many people are benefiting from your informational great videos!
thanks a lot for your work
Incredible easy to understand explanation about the importance of Mesh Flow, and Quad modeling, thank you so much for all your work!
Thanks Grant, always enjoy your clear explanations and insightful videos.
Most characteristic voice i have heard on RUclips. Keep it up man, You are helping so much
Thanks. Glad to hear
Best explanation I've heard. Clear and concise. More please :)
thanks. Yes there will be many more :)
These tutorials are an absolute treasure, thanks Grant :)
Glad you think so!
I was yesterday searching for this! Thanks mate I love your content!
Glad to hear thanks
IMO, modeling in quads makes it easier to visualize the topology.
It just makes it SO much easier to work with and unwrap :)
Very informative and easy to follow examples, great work!
Thanks :)
Thank you for this fantastic explanation🤩🤩
Great explanation. Every newcomer should watch this video, improves his actions right from the start. I didn't know this for a while, have created a detailed and good looking character - but it's topology was a mess beyond believe. Completely retopologized the character recently, now you don't get eye cancer in edit mode anymore.
This video appeared to me literally as I was needing this info. I was following a tutorial and thought I was being clever by using tris on certain corners. After all, my Computer Graphics teacher taught me all about said triangles and the entire classical rendering pipeline. Then I couldn't loop cut, I had no idea why and apparently the tutorial neglected to mention those only work on quads. Had to redo my entire mesh...
Thanks Grant, always enjoy your clear explanations and insightful videos. One thing I would add is the new focus on Boolean hard surface modeling, which of course is antithetical to quads.
Using Boolean modeling with a non destructive workflow is a superb strategy for concept design. It allows for multiple iterations, including client feedback cycles without the tedious focus on polyflow and strict adherence to quads.
Both approaches are valuable!
Yes very true
Great video! Thanks, Grant!
Thanks 😃
Thank you for this kind sir.
Nice video thankyou so much sir.
Thanks for this
been through a few of tutorials ( BTW they are all of this quality ) and this is like a light bulb going off in head. Maybe running to far ahead but think I 'got' this topology stuff. Thanks again.
good to hear
Very useful bro, thanks a lot
Thank you so much
Quads are gods, triangles are angels and a ngon is the weird fool of the village.
You get used to this once you start doing retopology. You will learn by doing mistakes. And oh boy, mistakes are many and they come quickly. But when you are fully done you are pretty much a pro.
You are topology master sir.... Addicted to your videos
Thank you Thank you..this is very much informative.
good to hear thanks
Nobody ever explains in tutorials why quads are so important, thank you
Triangle to stop a loop cut
Brilliant!
Nice, I knew what these were, but really had no idea about how they actually affect the mesh. I thought the reason to have quads was so the mesh unwraps clean, which I'd imagine is one reason? Thanks for doing more "noob" videos as I know you're experienced, these are best videos you do in my opinion.
thanks :)
Very useful and great timing as well. Just started focusing on good topology for subdiv hard surface modelling and it's been rather interesting to say the least. Not looking forward to retopology though haha.
😃
Thank you teacher!
Thank you very much. I'd like to see similar tutorials.
Thanks 😃. I'll do my best
hell yeah. So easy, how did I not see this reason before?
Thanks.
Thanks :)
Huge helpful
Amazing I was seraching a video on this topic and there is nowhere so good explanation like this :D , Maybe you can do a video when u have a lot of ngons how do you clear theme up :)
will do :)
If I'm allowed to add my piece, through my limited experience in the industry I noticed that triangles and Ngons create 2 major problems.
First if someone send me a model with loads of triangles (usually it's only triangles, Ngones are rather rare) if I need to do changes (and I usually do) I will have a hard time, it's because triangles and Ngones add "character" to the models topology, a character that first is not needed and second I have to waste time to understand and then brake it.
Quads work as a common language between designers, that's the way I see it, something like English.
And second I never landed a job (I haven't landed every job on the planet so feel free to share your experiences) where I had to use only one program, our workflow always demanded several programs, some where well known, some where custom made (oh god, horrible experience... I tell you) but most of them had serious problems if the mesh didn't had a clean topology.
Game engines are an exception tho, triangles are necessary, but it's usually the final stage and we never replace the original quad model in order to do changes easier.
All that said some times you need to brake the rule first in a situation like you demonstrated, or in order to lower the amount of polygons.
Other times you "brake" clean topology in order to have a cleaner, less confusing one.
Indeed that is all true from my experience also :)
@@grabbitt We are childs who play in similar parks then I guess :D
Would you say it's best to always have a copy of your model in quads, so you can always go back and make new changes? Then just export a new copy in triangles when you're making the game asset?
@@taylorhead9842 precisely yes. My scene in Max or Maya or XSI(good old times), sorry I have no Blender experience, is always in quads.
Usually I just auto connect the points to triangulate it before hand, I just don't keep a save of it (don't do that, it's just a bad habit that I have) or let the fbx exporter to do the job.
In a few rare cases I create a copy of the model inside the same scene, triangulate it and then I fix some areas that doesn't display properly in the game engine, so in this case I have both the quad and the triangulated model saved as a scene, it's super rare tho, I encountered a situation where I had to manually triangulate a model only 2 times in several years.
So yeah, my scenes are quads and my exports are triangles.
It is the same mindset with everything else actually, I always save in increments, in order to prevent corrupted save files and have a previous point where I can return to.
Say for example instead of randomly sculpting parts of my models, I sculpt in passes, sculp the whole model with one brush and then I use the next one, this way if I notice that something doesn't work or my directors send me feedback I can always revert to the previous stage without wasting any time fixing on top the problem (some people like to do this, I don't) or start from scratch.
I don't know if any of these makes sense, my English is @_#&# as you can tell.
:)
That was great. Thanks I'm a noob and never understood that.
TL;DR: Computers love tris, but blender is programmed to hate them.
Thanks
Tri's are hard to work with, and show seams. I am glad how Blender works.
Even game modelers work in quads and convert at tbe end of the process
Don't see how they "show seams" any more than quads. It all depends on how the modeler is working with them. Either way it's kind of pathetic how poorly Blender deals with them - It must be difficult making say, a retro-style model/videogame using blender due to that.
@@robfrydryck127 Also let it be known that sometimes you HAVE to work with triangles - Blender defaults to an n-gon when making a cylinder's top/bottom, for instance, but n-gons are kind of unusual to work with, and the only other option is.. You guessed it, a classic triangle-fan! The fact that blender's selection tools don't even really work well on that triangle-fan, despite it being one of two only real options for filling a cylinder's ends, is just disappointing.
@@maxwell_edison well you can also grid fill
Someone must have already explained this, but since you didn't seem to know the real reason for the triangles and quads:
The reason GPU pipelines use triangles, is that they are the smallet possible plane with 3 vertices and can be used to make any other shape. They require 3 vertices, but if you add only one vertice, you get a quad, that is basically worth 2 triangles (6 vertices worth of info in 4 vertices) etc. Every new vertice you add, will create at least one new triangle plane when you connect/close the mesh to another part, you get an extra plane, like 4 vertices can actually make 4 triangles/planes and is also the smallest shape with volume, if you close it. With quads you'd need 2 per newplane. So when you are making a quad, you are actually making 2+ triangles with every 2 extra vertices required to make one new quad
.
.
Each new plane also gives you access to new normal, and finer detail and effects
Since they can be used to compose anything and are so memory efficient, this is very "intuitive" to computers and extremely fast, since you can very heavily specialize in them, without being limited in any way
Hope this clarifies the issue a little, hope I didn't remember anything wrong, since I haven't programmed 3D pipelines in over 11 years (@_ @ )
Hi, Grand. Can U tell me please - on 7.14 red personage apearing on the screen. Why is 4 dots on the Faces after retopology? Just intresting)
How can I select all of the triangles in my model? or select all of the non-planar polygons? I don't see an obvious option for that. Thanks!
select by traits
That was interesting, I'd love a tutorial and what to do to clean up triangles or n-gons. That's a problem I have with retopology.
I use all the tricks to make loops that turn the loop cuts back on themselves, but then I end up with retopology that deform the mesh and makes it not smooth.
Like when trying to model a hand. You may have a lot of loops and stuff near the fingers but when you get to the shoulders you're stuck trying to reduce vertices and it's hard. I have a hard time with that.
it can be tough but with practice you start to get the idea
4:27 , if a giant triangle(or a group of triangles) was at the top, things would subdivide ALOT better than having that giant ngon sitting there. I would've deleted that entire ngon, loop selected those top edges, pressed the 'f' key, then I would've triangulated the entire top face and then subdivided it.
yes that would be better to tidy up.
I was curious to se the subdivision surface in other objects. Besides that, your example with animation didn't show much. But from this video we can have a good notion about why to use a quad.
Yes I don't think I did well at explaining the animation bit. Hopefully the gif helped to explain a little. Thanks for the feedback
Can u do video about changing or getting the flow in a direction like that :)
I will try my best yes
I heard Maya and 3DS Max model with triangles.. so do they have a similar function as a loop cut? Does it require more skill to model with tris?
They are just he same as blender as i have described in the video. They have the functions to mode with all three but it's best to stick to quads
0:41 Short for “quadrilateral”.
The reason why things are allways triangles, at the end:
Create a plane and lift up one corner in edit mode.
Then, make them triangles (ctrl+t) and select the diagonal edge.
With shortcut W, you can rotate it (switch corners).
As you can see, when a quad is not flat, it's shape is undefined.
It is impossible to know what a quad looks like if it's not flat.
A computer cannot know how to shade it or shape it.
So, it will always make triangles, even when it merely looks like a quad.
An uneven quad will be very good at hiding how it actually looks.
I built my own 3D printers; when I would have to print a quad like this,
I will not get the expected result, because it allways prints triangles.
So , if you really need to know what a model will look like, you
have to make all polys, triangles, in order to avoid mistakes.
At least, you avoid buggy shading, especially with low poly models.
yes indeed :)
3:50 You can still see all the weird waviness of the subdiv in that top surface, but since it’s all in the plane of the top face, it doesn’t make any difference in the render.
Unless you are trying to assign different materials to different parts of the mesh...
Question! Is it okay to have quad's vertex with more than the minimal four edges connected to it?
I've seen it very often as a minimal neccesary because of the topology.
no that's fine they are called poles
@@grabbitt Very well, thanks a lot!! keep up the good work.
I'm still a beginner and figuring out how to cut properly in order to keep quads is really challenging for me, I feel like it's a puzzle I'm not really good at. Some shapes are fine, others seem impossible.
Don't worry too much you'll get there with practice and it's probably not as important as you think
What about for 3D printing? Can tris and ngons cause problems in that field?
there ok
I was mostly interested in learning why they're bad for animation. I'm glad you went into animations a bit, but I would have liked a more detailed explanation. Another thing I read about is that triangles and Ngons can cause graphical artifacts of some sort, other than just deforming an object badly.
EDIT: Fixed grammar.
Good
Ur a god bro
Thanks :)
I'm doing a game prop, let's say it's a 🗡️ (sword). So for modeling the proper would be work it with quads, but should I convert quads to triangle once I finish the mesh? Sorry I'm new with the subject.
You don't have to convert at the end
Ngon... where I'm from that name is only mentioned in hushed tones and closed circles.
:)
Not sure if you’ll see this, but I’ll try anyway. I want to go into the game industry as a hard surface modeler. When showing my work to companies, are seeing ngons on your wireframes frowned on (assuming it’s on a flat face that where the mesh wont get deformed)? I have a few models I’ve built and I have ngons due to some Boolean cuts and I need to know if that will affect the hiring process. Thank you!
It depends on the company and their expectations
@@grabbitt thanks for the reply! How nice that you respond to even the older vids. Cheers!
so ngons are good for flat surfaces I was thinking why people don't use them for simple things like roads but seems like it would be really good just to use ngons on roads as you keep the polycount low on more coved road and be more optimized for games?
Yes but remember everything is converted to triangles when rendered
Computers are better at doing simple processes loads of times, for example rendering with triangles, arithmetic in binary format.
Humans are better at doing just a few steps which can be to some extent complex, for example modelling with quads, arithmetic in decimal format.
Question, once someone gets a model from there and imported to any 3D software Can you still remodel it despite it being tris?
Yes
@@grabbitt how can you remodel a tri model that was download? I tried to turn it to quads but it just become a mess of edge loops.
it is better to convert a quad into a triangle...by taking 2 vertices close to each other rather than importing a triangle...in that way we can still add loop cuts!
not quite sure what you mean by importing a triangle. I would just convert a quad to a triangle if i had to divert a loop cut
Quads are easier for animation, shaping, selecting rings, etc.
Can we use ngons for objects like buildings....??? Will it cause any error?
You can use them on flat services
thank u
Hi Grant, I follow some hard surface modelers here on RUclips (I won't name names). They use a strong ngon based technique. Basically the internet have so many different opinions over the topic "quads vs ngons". What do u think about it after 4 years from this video? I'm really confused about it.
what ever works for your output is absolutely fine. It's becoming less important in many cases
thx helped a lot although i am on 2.8
lol k
Helped me and I'm on 2.9
i tought you will mention triangulate and tris to quads functions too :p sometimes they can help a lot
Very true
Thx. The way I kinda come to understand it is blender wants to average out from one edge to the opposite edge. But with 3 or 5+ edges there is no opposite.
yes that's a good way of looking at it
@@grabbitt a problem I've been having is adding in detail without messing up the mesh, say on a sphere. I wish you could add a edge loop that wouldn't destroy something like a sphere.
I've been using a shrink wrap and another sphere to get around it. Any better suggestions?
yes. Don't use a sphere use a subdivided cube :)
@@grabbittoh yes that's what I meant. But I just meant more general If you're adding details on using sub d.
Is that how you would do it to keep the over all shape. Using a shrink wrap on the duplicate to keep the over all shape?
@@SlyNine yes
is it okey for building to had ngons??
Yes
@@grabbitt thank you so much for the reply ^^.
I try to avoid tris at all cost, but in low poly and sometimes even in mid poly modelling they appear to look better than quads, even when subdivided. I don't indulge in them just because 'they look good' but sometimes I see models from good modelers that have tris and work great. What should I do?
Whatever works for you
how to get rid of 5 vertex ngon and make it quad?
It's pretty awkward
It depends on the edge flow you are trying to achieve, but you will be adding more vertices. You can split it by adding a 6th vertex. Similarly you can add a vertex to the middle of the nGon, then add vertices on 3 of the edges and alter the edge flow. If the edge flow doesn't matter, just create a triangle.
The programs make the quads works like two triangle quads anyway. And like a comment some body made, triangles dificult de edition of topology. If you need to subdivide, the triangled mesh become a mess!
this might be a silly question, but what exactly is the number of polygons, is it the number of faces or triangles ?
Yes it can be either
@@grabbitt Ok. But what if I want an object which is less than 10.000 polygons, should I then rely on the number faces or the number triangles in blender ? im a bit confused by those two and polygons.
@@blomma4304 if in doubt go by the triangles
Чел, создавший субтитры, ты...
You could also have showed what it does to textures. If you create a UV of your bend block and put a checkerboard texture over it to make it obvious one would see that the checkerboard gets distorted in that area where the triangles are. This would be really hard to sort out in UV mapping since that will always lay out the triangles flat and distort it when bend while with quads you can get a nice flat square as a UV map of the whole object which you can align equally on your checkerboard texture. Thus using quads prevents the occurrence of odd looking texture distortions.
2:34 That "cylinder" of yours is more of a right hexagonal prism.
Prisms have a polygon as their base, but cylinders use circles
I personally only let triangles be if it's part of a spot that don't move. Like the ears
makes sense
let me see if I got it right:
triangles are the base for everything yet very situational.
squares are the flesh and bones of modeling.
"Ngons" are (mostly) useless.
Kind of
*end guns*
The thing is that an N-gon is nothing but a group of quads with an odd triangle. But game engines sees nothing but triangles anyway, even when the draw primitive setting is on quads. So this may be a simple case of splitting hairs here.
yes they all become triangles eventually. It's more about the aid to modelling
@@grabbitt Very true. But even in modeling, there's always an 'ugly' part of the model unless you are making a basic cube ,which is perfectly boring
Older versions of Blender didn’t have N-gons, they had “F-gons” instead. These were what you describe: under the hood they were just made out of quads and triangles. There was much celebration when Blender finally added true N-gons in place of the F-gons. I think this came in as part of BMesh.
You're only allowed to model in quads! (twitch)
das twuuu
I see
Stray ngons and tris are like hangnails.
I think the important bit is to have a topology that supports your workflow with the model. Tris and even ngons can be a part of that, they just have to be incorporated in a way that supports that workflow
Why do you have Russian subtitle? 🤔
Someone did them for me
@@grabbitt 😯
Confirmation: distortion on the bent thing IS visible here on RUclips.
:) good
You are a superman in Blender. …*……V………^
Thanks :)
That bendy knee example was bad, the side examples segments were too narrow to work at that angle.
It doesn't matter tho. Elbows and knees aways have that straw like problem when skinning that always needs to be fixed with corrective blend shapes or other joints with minor weight(if the level of detail of the rig requires it) . Iker de Los Mozos has a real good quick demonstration of how to set a performance enanched solution rig for this problem on his instagram
NGons, the N stands for NOPE!
triangles are ok, but never NGons, if you have to export to any game engine, it will go wild
In my limited experience Unity has only had an issue with ngons when I needed to merge vertices. Something like an ngon wheel hub will import fine, but a face with a hidden 0 length side where the two vertices overlap will trigger warnings in the console.
Honestly, to an amateur like me, all the problems with triangles you describe are just problems with how the software deals with them (or, in these cases, doesn't even try to).
I've tried doing low-poly stuff, but I just get bottlenecked into problems with "quads" doing things to the triangles that doesn't make sense, and not allowing me to control the triangles to stop it.
they are called polygons ...sheesh, ngon.