Retopology A Detailed Guide - What is Retopology & Why Do We Need It?

hello and welcome to gabit media i'm grant abbott and in today's video we're looking at what's re topology and why do we need to bother re-topologizing so it's a theoretical look at retopology for complete beginners we'll be looking a bit at tries quads and n-gons and what's the difference and breaking down terms such as clean topology and edge flow if you want to know how retopology fits into the workflow of creating models then i suggest you look at my how to make amazing models for film and games video which talks about the process of making models in their entirety so you can understand where retopology kind of fits into the workflow now i'm not going to talk about the actual process of how you read apologize if you want to know that process then follow my learn retopology playlist links in the description also i'll be doing another video following this about the different automated tools that make retopology much easier some that are built into blender others that are free and others that are paid for so look out for that and i'll put the link in the description once i've done that as well if you like what i do and want more educational content such as this then check out my playlists and my website for more free courses so what is topology and why do we read apologize topology is the way the faces are mapped out on the objects so they kind of have a flow to them and good topology flow which we'll talk about later will be better for modeling animation weight painting rigging and even texture painting so topology is simply the way the faces are linked together across your model one of the most important reasons to re-topologize is to reduce the polycount sometimes known as the face count and that's how many faces you have on your model a common workflow for making game assets is to sculpt the objects which makes them extremely high poly or really high poly count so lots of faces as an example let's take this beast to character here so this is a recent sculpt and you can see the time lapse of me sculpting this in a different video links in the description but you can see over the left hand side here it's got over four million faces and if we zoom in to some areas you can see all the details with the bumps and this is far too dense especially for things like games as a general rule for games a detailed character with clothing and other assets let's say armor and so forth would be around 20 to 30 000 faces that does depend on the game and the platform but most sculpted meshes just like this are commonly around 4 million faces they can go up to about 20 million even but this means really long render times very large files texturing is a lot harder texture painting is almost impossible unless you use vertex painting which limits your options considerably so reducing the poly count is very important if you want to work in the industry and probably will be for a long time into the future we need to massively reduce the poly counts and make them more optimal as assets for games and films and so on so what are the different types of topology and what does it mean by clean topology well firstly there's triangles quads or n-gons and i do talk about this in a different video called quads tries and engones but i'll give you a quick overview now as the name depicts it's how many vertices or edges a single face has all meshes will be built up with at least one or all of these and there's different reasons for using them so if i select my n-gon at the end here and go into edit mode with tab that means i can edit the individual vertices faces and edges and you can see i'm in edit mode up here now at the moment it works fine if i move around it you can see that it's working and rendering just fine and that's because it's planar that means it's flat however if i grab a vertex like this and press g then zed to move it upwards now i start moving around to here looks a little bit strange and then i'll move around to here and we can see it's distorted the shape let's try moving this one down g then zed and blender is having a hard time figuring out that there should be a sort of curve down here and joining them up it's basically converting it into triangles when it shows it to me so there's a triangle down here and a triangle down there so it's not really an end con at all blend is actually splitting up into triangles to render it and that's what happens with any faces they all get converted to triangles like this at the end if i come back into object mode choose my quad this time and back into edit mode and move one of those corners up g then z you can see a similar things happening down the middle it's creating a triangle down here so that it can render one side and another so why do we bother with n-gons and quads why don't we just model in triangles well modelling in quads is really important when you're creating models because it's so much easier to model let's go to edge mode with two on my keyboard and extrude this out now if i want to edit this at all i can create a loop cut in it by control r and produce a loop cut move it up and down i can do a loop cut this way which goes through all these edges i move that downwards let's say i can bevel this and make it curved i can select edge loops like this with alt left click maybe bevel that with ctrl b and create some curves and you can see how we can build up a mesh nice and easily using quads and i'll select one in the middle here and press ctrl x to dissolve it that means we've got a weird sort of square in the middle you can see how it's not really working and that is now an ngon and can you see how it's gone a bit strange on the other side there because it doesn't know how to render it so it's kind of making a triangle down here to try and render it now if i try and do a loop cut down the middle control r i can't it stops as soon as it gets to the end gone so that nice easy flow of modeling i was doing of creating loop cuts like this is stunted by this end gone so i'll undo that what i'll now do is go to vertex mode and join these two together so j to join them together and press control r again that's exactly the same it won't go through the triangle it will go through these quads here but stops when it gets to the triangle and that's why we don't model with triangles even though it's all reduced to triangles eventually we model in quads to make it much easier you can see actually that if i create a loop cut there suddenly i have a quad here and i can actually control r and go through this quad like this if i create one the other side and press control r i now have a quad-based mesh and i can go through it but it's strange how the triangle kind of diverts it into different directions and that is called edge flow and it's the flow of your edges which is important for creating these loop cuts through your objects these loop cuts are really useful for adding extra detail let's say i create one in here and press g then z and pull that down can you see how we got a sort of detail going through here now and we can increase that detail with maybe a bevel control b and it's all looking pretty crazy if i put a subdivision surface modifier on that we've got a really interesting detail working through that and that's because this is a higher resolution section here and our subdivision surface is flowing through that so often we want to add more detail to specific areas such as eyes perhaps for when people blink and it's really nice to be able to add a quick loop cut to increase the amount of faces in that area and then we can add more detail we can deform it easier for animations and so on more about that later though you can also see here that i've added a subdivision surface modifier which adds an element of detail and smooths out your mesh and they work best with quads so a good rule is to stick with quads as best you can when you're doing your modeling but it's important to bear in mind that all meshes are converted to triangles in the very end and some people when they're doing very simplistic game models and so on will actually model in triangles to try and keep everything really low poly precise and optimal and accurate so whether you're going into a game engine or you're rendering in cycles or ev what you're seeing is always a triangulated mesh so all quads and n-gons get converted to triangles when rendering but like i say it's much easier to model when you're using quads so what about dirty meshes well topology that is classed as clean tends to be all quads but clean topology can also mean the topology follows along the natural lines which generally means the creases of an object this is called good edge flow so following the edges of the object as we can see on this dragon's head around the base of the horns for example or in the eyes and nostril crevices and this is helpful for things like animation and marking seams for texturing let's take a closer look at animation okay so here i've got two sort of rectangular posts and they look fairly similar one has very bad topology if i select that and i'll go to wireframe so you can see the topology on top and i've sculpted this slightly and used a decimate modifier which we'll talk about in a later video but you can see the sort of topology that it's created it's really messy and not all quads if i go into edit mode and press ctrl r to do a loop cut you can see it goes through some of these but obviously it's stopping where there's triangles and end guns so doing any more modeling with this will be a pain and we'll have some problems when it comes to animation okay so then there's this one and i'll show wireframe on that as well and you can see it's the same sort of thing but much cleaner topology and again if i want to do something to this model into edit mode i can do some loop cuts and things through it and extend it nice and easily so it's much easier to model but what about animation okay so i've given each of these an armature and i'll come into these next two a bit later but i can come into here go to pose mode select this top bone and rotate it in the x-axis so it bends with my object but can you see how bad the topology is and what happens when i move it like this it distorts and goes all over the place i'll quickly turn the overlays off so you can see the distortion and what's happening it's stretching the mesh and making a real mess overlay's back on however if i go to the next one into pose mode select that top one rotate around the x-axis and bend it around because we have cleaner topology we can see that it's much nicer it deforms how we'd hope and if i turn the overlays off you can see that deformation there working well well we can take that even further i'll turn the overlays back on and i'll take you to this one along here let's show the wireframe for that now where the bend is i've got more loop cuts that means when i go into my bones into pose mode and rotate this in the x-axis the deformation looks a bit better let's turn the overlays off again you can see that we've got a much smoother bend so putting extra topology around the middle here is helping us with that deformation and that shows that understanding topology and where to add extra topology can really help with your animations let's go to this last one here and i'll put the wireframe on for that and we'll go to the bones into pose mode rotate around the x-axis now this one's slightly different if i come around here we can see the edge i've actually got a triangle in there but let's turn the overlays off and see how well it's deforming it's not that dissimilar to this one here but this one actually has less polygons and a triangle within it i'll rotate it back up and hide the armature for a moment so you can see that this one has a triangle on the side here and kind of an extra face at the back here so it's an interesting case where you can actually utilize modeling in tries or triangles to get the same results with the animation but with less polygons and this is often a technique used for low poly modelling we are trying to be as optimal as possible by going as low poly as possible for things like mobile games but you still want to keep its integrity when it bends and distorts so back to the bone rotate round the x and you can see it does a good job with less polygons so there's dirty topology which just doesn't work for animation cleaner topology which works but it's not optimal then we've got slightly more optimal topology and how we can add topology where there'll be bends then we've got super highly optimized for low poly gaming and things like that where we've reduced the topology for optimization so i've talked a lot about organic meshes like monsters and things but what about hard surfaces well clean topology is also important for hard surface modeling as well it's very common for people to use things like booleans to create objects which makes a lot of mess take this object for example there's a sphere here that's cut into this cube and that's using a boolean modifier which is really common with hard surface modeling and here i've applied the boolean modifier you can see that we've got a huge end gone here here and here if i go back to object mode it looks around at the moment but what if i want nice sharp edges down here with a bit of smoothness let's right click shade smooth oh we've got lots of anomalies so maybe we can tidy those up with something like a subdivision surface modifier that smooths it out oh and we've got a big huge mess there's ways we can sort this out we can try adding a bevel modifier and we'll move that above the subsurface and that's helping a bit but what we actually need to do is start adding some topology in here so if i bring the knife tool in i can start cutting and you can see as soon as i start making these cuts our topology down this corner gets a bit better let's just go into object mode and see what that looks like so i'd need to do that around my mesh but you can see it's a big mess so even with this sort of boolean phase we still need to know a bit about topology to understand that big end guns like this can cause problems especially when it comes to subdivision surface modifiers and incidentally to clean these sort of meshes up it's usually a case of adding more topology for it to be able to define those edges a bit better it's not quite as simple as this and you'd want to give it help and support around these edges around here and merge some of these vertices together that are causing us problems such as these here but you can see a general sort of cleanup once we add a bit more topology so artists making hard service models often start by using booleans to create the overall design and then they read topologize the mesh for texturing and games and so on so it follows the same sort of workflow as the sculpt in regards to starting with a high poly mesh and then retopologizing to simplify it therefore an understanding of topology will not only help your hard surface look flat and clean when using booleans and bevels and so forth but it's also still needed to reduce the face count of the models for multiple uses now i keep sort of referring to the sculpting workflow and another reason for root apologizing is so you can go further with your sculpting tools like dyn toppo are really great because you can create amazing creatures and odd shapes freely and expressively dyntopo will keep adding topology when you stretch and pull meshes so it is really nice to start off a sculpt like this however when it comes to adding detail dyn toppo doesn't do so well you can't go to a really high resolution because your computer will start to lag as it tries to recreate topology every time you press down on your brush to get more detail from your scopes it's best to re-topologise and put the detail through a multi-res and you can go much further in terms of polycount to get some really fine detailed sculpts also with good topology you can choose the areas where you need most faces so you can add more things like loop cuts and faces to areas such as the face of your model or the hands or any key areas where you need more detail and there's going to be more focus with something like dyn topper you have more of an even distribution in terms of the topology and faces and therefore the density of your mesh has to be very dense in every single area in order to add those details the multires tool is really clever with this you can copy the details you have from something like a dye and toppo or any sort of sculpt and you can put that into the higher subdivisions whilst keeping the original retopologized mesh nice and low and you can bake from one to the other to get the detail that may not make much sense to beginners but if you look up things like normal maps and cavity maps you'll understand more about that process and how they get low poly meshes in games to look really detailed it's a relatively complex process but if you want to learn more about sculpting in more detail cg boost sculpting course is very in-depth and i thoroughly recommend it also if you want to know about sculpting detailed characters then there's my character course which takes you through how to sculpt a game-ready character in detail so follow the links in the description for both of these and a discount on the character course so hopefully that explains what's meant by retopology and why we need to re-topologize in the next video i'll talk about automated tools for retopology some are really good some are really bad and some can get pretty ugly let me know your thoughts and comments below thanks for all the support those that donate those that watch an advert those that sign up to my patreon it's all very much appreciated thanks for watching and i'll see you next time

Channel: Grant Abbitt

Views: 149,435

Keywords: understand, texture, paint, learn, blender, tutorials, 3d, art, graphics, game, material, guide, easy, painting, how to, gamedev, topology, retopology, edge flow, mesh, quads, tris, ngons, retopologize, building models, game models, models for games, 3d models, blender 2.8, 3d modeling, blender 3d, theory

Id: S4YNiImIgPs

Length: 16min 44sec (1004 seconds)

Published: Thu Apr 29 2021