From the course: 3ds Max 2025 Essential Training

Understanding subdivision surfaces - 3ds Max Tutorial

From the course: 3ds Max 2025 Essential Training

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Understanding subdivision surfaces

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- [Instructor] Subdivision surface modeling is a technique to create smooth flowing surfaces such as a character, a creature, or even the soft cushions of this office chair. In this scene, the seat cushion is an active open subdiv object. That means I can change its level of detail at will while preserving its overall shape. The other objects have all been baked or converted to editable poly, and although the bottom seat cushion looks round and smooth, it does not appear to have as many polygon edges. Well, that's just due to the display mode that we're in. Let's investigate, select that seat cushion. Go over to the modify panel, and we see that the stack consists of an editable PolyBase object. Above that, there's a symmetry modifier to reflect the polygon surface to the other side. That way we only have to model half of the object. At the top of the stack is the open subdiv modifier. Its function is to subdivide the polygons on the base object. Not only that, but it averages the angles among the new subdivided polygons to smooth out any jagged corners. If we disable that top modifier by clicking on the visibility or eye icon, we see the original polygon mesh. That is what is known as a control cage. It's merely a means to an end. We're never going to actually render or export this low level of detail mesh. We use that as a control cage or a tool to sculpt with subdivision surfaces. Okay, I'll re-enable open subdiv. If we want to see the actual level of detail or the individual polygons after the subdivision, we can disable this option over here. ISO line display. Turn that off, and now we're seeing all the individual subdivided polygons on the object. The most important parameter of a subdivision algorithm is its number of iterations or number of repetitions. That's the number of times the mesh will be subdivided. If we change the number of iterations, we increase or decrease the level of detail. I've got the polygon statistics for the selected object displayed up here. Remember that the hot key for that is seven and that in order to see the statistics for the current selection, we need to enable that in the viewport configuration dialogue. Let's bring the iterations value down by clicking on the spinner with an iteration of one, we see a blockier object, with iterations set to zero we see the original control cage or the original polygon mesh. As we increase the iterations value, watch the polygon count up here, bring it up to one, and we have about four times as many polygons bringing it up to two, and we quadruple the number of polygons. Again, if the object is built out of all quadrilaterals, then each iteration will quadruple the polygon count. An iteration value of two or three is usually optimal. If I take the value up any higher to like four or five, that's really overkill. That's way too dense of a polygon mesh. We don't need that and it's not improving the fidelity. The optimal value here is actually two, so I'll bring that back down to what I had. Subdivision services have been implemented in several ways in 3ds Max. The algorithm has been around for a while, and the design of the software implementation has evolved over time. The open subdiv modifier is generally the optimal workflow because it has the best performance and the best compatibility with other applications. It's based upon an open standard, the open subdivision surface standard. We can also subdivide meshes with other modifiers. In the modifier list, we have several other subdivision modifiers. We'll see there's something called mesh smooth. There's also one called turbo smooth down here, and additionally one called HSDS that stands for hierarchical subdivision surface. Any of these will perform more or less the same function, but open subdiv is faster and better, so I'm not recommending that you use those other modifiers, and in fact, if you see a tutorial that references those other modifiers, I recommend that you use open subdiv instead. Subdivs are also built directly into the editable poly object and the edit poly modifier, and there they're called nurms N-U-R-M-S and that built in subdivision algorithm can come in handy sometimes, but in most cases, the workflow I'll be demonstrating with the open subdiv modifier is the most effective and flexible. That's a basic introduction to the concepts of subdivision services and how they're implemented in Max.

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