From the course: 3ds Max 2019 Essential Training

Understanding subdivision surfaces - 3ds Max Tutorial

From the course: 3ds Max 2019 Essential Training

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Understanding subdivision surfaces

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- [Narrator] Subdivision Surface Modeling is a modeling technique to create smooth, flowing surfaces such as a character, creature, or even the soft cushions of this office task chair. And what we see in this scene is one of the objects in darker gray, the seat cushion, is an active open subdiv object. I can change its level of detail at will. The other objects have all been baked or converted into editable poly or editable mesh. To see this a little bit more clearly, let's enable wire frame unshaded or edged faces with F4. And although the seat cushion at the bottom here looks rounder and smoother, it doesn't actually appear to have as many polygons. Well, that's an illusion. It's actually because of the display mode we're in. Let's investigate. Go over to the modify panel. And with that seat cushion selected, we can see that the stack consists of an editable poly, a symmetry modifier to reflect the polygon surface to the other side, and that way we only have to model half of the surface, and then at the to is the open subdiv modifier. And what that's doing is it's adding more polygons and averaging the angles among those polygons to smooth out any jagged corners. If we disable that modifier then we see the original polygon mesh. I'll re-enable open subdiv. And if we want to see the actual level of detail, we can disable the iso line display switch here. And now that's the actual level of detail after it's been sub-divided. If we change the number of iterations here we will increase or decrease the level of detail. At any iteration level of 0, we see a mesh that's identical to the original polygon mesh, or a control cage. And as we increase the iteration's value, we get more detail on the surface. Alright, let's go back to basics and start from just a box so that we can get some key concepts around subdivision surfaces. I'm going to reset 3ds Max from the file menu. I'm not saving any changes. And just create a box from the create panel and go into the modify panel and set its length, width and height all to 100 centimeters. Back out a little bit. Looks like I've got selection brackets. With the J key I can turn those off. And turn on edged faces with F4 once again. And now we've got a simple cube with only six faces. And we can verify that by looking at the statistics in the view port. Press the "7" key on the keyboard and it says we've got 12 polygons, so that counts each one of the triangles. So each one of these quadrilaterals is composed of two triangles, so six sides times two is 12 polygons, or 12 triangles. Now let's add the open subdiv modifier from the modifier list, scroll down a little bit, open subdiv, and it has a default iteration value of 1. And now we have 24 polygons instead of 12. We've actually doubled the number of triangles. As we increase the iterations, we'll see that number jump, and now we've got 96 triangles. If we want to see the actual level of detail once again, we can disable iso line display. And as we increase that value, once again we're getting more and more detail. And with an iterations value of four, we already have over 1,500 polygons. We went from 12 to 1,500. Usually you want that iterations value to be around two or three for most applications. Alright, now we understand how that works. We can disable the statistics with the "7" key once again. One of the most key considerations with subdivision surface modeling is quadrilateral polygons. You want to have quads everywhere if possible. Try to avoid polygons with more than four sides, and try to avoid triangles if you can. I'll show you an example. Just go over to the create panel and create a standard primitive cylinder. Click and drag. Drag up to set the height. Right click to exit. Go to the modify panel and add an open subdiv modifier. And it looks quite odd at the top and bottom. And this is not really a good situation. If we turn iso line display off, we can see that it's actually quite ugly geometry. As we increase the number of iterations we can see that this is going to be very difficult for us to work with if we want to actually shape this in a model. So I'm going to go into the cylinder parameters and make a couple of changes here. Most notably I'm going to set the number of sides to a multiple of four, and that will make it easy for me to divide the cap of the cylinder into quadrilaterals. Alright, so we can see this is happening. Let's disable open subdiv and set the number of sides to 16. And in order to do some real editing to this we'll actually need to convert to editable poly. So with open subdiv still turned off, I can right click and convert to editable poly. And since the subdiv modifier was not active, the object got baked in that state and now it's an editable object. So let's re-add the open subdiv modifier and see what we can do here to clean up this geometry. Go into the editable poly and enable show end result. Now we're just going to use the cut tool. It's easiest to use the cut tool if we can see the vertices so we can go in to vertex sub object mode. And grab the cut tool. And we can access the cut tool from the modify panel or from the modeling ribbon. I'm just choosing to do it from the modify panel, and we've got the cut tool down here. Click on cut. And then just orient in the view so that we kind of know which way the axes are pointing so we can make our cuts appropriately. I'm just going to cut across here, and as we do that, we can see that the topology is changing. And once I've got one edge cut then I can right click and do another one, right click to exit, and I'm just chopping through trying to make some quadrilaterals here instead of those triangles. And after just a few cuts we can see that we've substantially improved the topology here. I can exit out of cut, exit out of sub object mode as well, go up to the top of the open subdiv modifier and disable iso line display. And we can see that there's a huge difference in the quality of the topology of the top where I actually went to the trouble of using the cut tool to chop everything up into quadrilaterals. And that is a best practice working with subdivision surfaces. Try to avoid any polygon with more than four sides or triangles if you can possibly help it. And those are some basic concepts around subdivision surfaces.

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